defineClass vs native unsealed

Benchmark created by Daniel Fielder on


Setup

var COMPILED = false;
    
    /**
     * Base namespace for the Closure library.  Checks to see goog is already
     * defined in the current scope before assigning to prevent clobbering if
     * base.js is loaded more than once.
     *
     * @const
     */
    var goog = goog || {};
    
    
    /**
     * Reference to the global context.  In most cases this will be 'window'.
     */
    goog.global = this;
    
    
    /**
     * A hook for overriding the define values in uncompiled mode.
     *
     * In uncompiled mode, {@code CLOSURE_UNCOMPILED_DEFINES} may be defined before
     * loading base.js.  If a key is defined in {@code CLOSURE_UNCOMPILED_DEFINES},
     * {@code goog.define} will use the value instead of the default value.  This
     * allows flags to be overwritten without compilation (this is normally
     * accomplished with the compiler's "define" flag).
     *
     * Example:
     * <pre>
     *   var CLOSURE_UNCOMPILED_DEFINES = {'goog.DEBUG': false};
     * </pre>
     *
     * @type {Object.<string, (string|number|boolean)>|undefined}
     */
    goog.global.CLOSURE_UNCOMPILED_DEFINES;
    
    
    /**
     * A hook for overriding the define values in uncompiled or compiled mode,
     * like CLOSURE_UNCOMPILED_DEFINES but effective in compiled code.  In
     * uncompiled code CLOSURE_UNCOMPILED_DEFINES takes precedence.
     *
     * Also unlike CLOSURE_UNCOMPILED_DEFINES the values must be number, boolean or
     * string literals or the compiler will emit an error.
     *
     * While any @define value may be set, only those set with goog.define will be
     * effective for uncompiled code.
     *
     * Example:
     * <pre>
     *   var CLOSURE_DEFINES = {'goog.DEBUG': false};
     * </pre>
     *
     * @type {Object.<string, (string|number|boolean)>|undefined}
     */
    goog.global.CLOSURE_DEFINES;
    
    
    /**
     * Builds an object structure for the provided namespace path, ensuring that
     * names that already exist are not overwritten. For example:
     * "a.b.c" -> a = {};a.b={};a.b.c={};
     * Used by goog.provide and goog.exportSymbol.
     * @param {string} name name of the object that this file defines.
     * @param {*=} opt_object the object to expose at the end of the path.
     * @param {Object=} opt_objectToExportTo The object to add the path to; default
     *     is |goog.global|.
     * @private
     */
    goog.exportPath_ = function(name, opt_object, opt_objectToExportTo) {
      var parts = name.split('.');
      var cur = opt_objectToExportTo || goog.global;
    
      // Internet Explorer exhibits strange behavior when throwing errors from
      // methods externed in this manner.  See the testExportSymbolExceptions in
      // base_test.html for an example.
      if (!(parts[0] in cur) && cur.execScript) {
        cur.execScript('var ' + parts[0]);
      }
    
      // Certain browsers cannot parse code in the form for((a in b); c;);
      // This pattern is produced by the JSCompiler when it collapses the
      // statement above into the conditional loop below. To prevent this from
      // happening, use a for-loop and reserve the init logic as below.
    
      // Parentheses added to eliminate strict JS warning in Firefox.
      for (var part; parts.length && (part = parts.shift());) {
        if (!parts.length && opt_object !== undefined) {
          // last part and we have an object; use it
          cur[part] = opt_object;
        } else if (cur[part]) {
          cur = cur[part];
        } else {
          cur = cur[part] = {};
        }
      }
    };
    
    
    /**
     * Defines a named value. In uncompiled mode, the value is retreived from
     * CLOSURE_DEFINES or CLOSURE_UNCOMPILED_DEFINES if the object is defined and
     * has the property specified, and otherwise used the defined defaultValue.
     * When compiled, the default can be overridden using compiler command-line
     * options.
     *
     * @param {string} name The distinguished name to provide.
     * @param {string|number|boolean} defaultValue
     */
    goog.define = function(name, defaultValue) {
      var value = defaultValue;
      if (!COMPILED) {
        if (goog.global.CLOSURE_UNCOMPILED_DEFINES &&
            Object.prototype.hasOwnProperty.call(
                goog.global.CLOSURE_UNCOMPILED_DEFINES, name)) {
          value = goog.global.CLOSURE_UNCOMPILED_DEFINES[name];
        } else if (goog.global.CLOSURE_DEFINES &&
            Object.prototype.hasOwnProperty.call(
                goog.global.CLOSURE_DEFINES, name)) {
          value = goog.global.CLOSURE_DEFINES[name];
        }
      }
      goog.exportPath_(name, value);
    };
    
    
    /**
     * @define {boolean} DEBUG is provided as a convenience so that debugging code
     * that should not be included in a production js_binary can be easily stripped
     * by specifying --define goog.DEBUG=false to the JSCompiler. For example, most
     * toString() methods should be declared inside an "if (goog.DEBUG)" conditional
     * because they are generally used for debugging purposes and it is difficult
     * for the JSCompiler to statically determine whether they are used.
     */
    goog.DEBUG = true;
    
    
    /**
     * @define {string} LOCALE defines the locale being used for compilation. It is
     * used to select locale specific data to be compiled in js binary. BUILD rule
     * can specify this value by "--define goog.LOCALE=<locale_name>" as JSCompiler
     * option.
     *
     * Take into account that the locale code format is important. You should use
     * the canonical Unicode format with hyphen as a delimiter. Language must be
     * lowercase, Language Script - Capitalized, Region - UPPERCASE.
     * There are few examples: pt-BR, en, en-US, sr-Latin-BO, zh-Hans-CN.
     *
     * See more info about locale codes here:
     * http://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers
     *
     * For language codes you should use values defined by ISO 693-1. See it here
     * http://www.w3.org/WAI/ER/IG/ert/iso639.htm. There is only one exception from
     * this rule: the Hebrew language. For legacy reasons the old code (iw) should
     * be used instead of the new code (he), see http://wiki/Main/IIISynonyms.
     */
    goog.define('goog.LOCALE', 'en');  // default to en
    
    
    /**
     * @define {boolean} Whether this code is running on trusted sites.
     *
     * On untrusted sites, several native functions can be defined or overridden by
     * external libraries like Prototype, Datejs, and JQuery and setting this flag
     * to false forces closure to use its own implementations when possible.
     *
     * If your JavaScript can be loaded by a third party site and you are wary about
     * relying on non-standard implementations, specify
     * "--define goog.TRUSTED_SITE=false" to the JSCompiler.
     */
    goog.define('goog.TRUSTED_SITE', true);
    
    
    /**
     * @define {boolean} Whether a project is expected to be running in strict mode.
     *
     * This define can be used to trigger alternate implementations compatible with
     * running in EcmaScript Strict mode or warn about unavailable functionality.
     * See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions_and_function_scope/Strict_mode
     */
    goog.define('goog.STRICT_MODE_COMPATIBLE', false);
    
    
    /**
     * Creates object stubs for a namespace.  The presence of one or more
     * goog.provide() calls indicate that the file defines the given
     * objects/namespaces.  Provided objects must not be null or undefined.
     * Build tools also scan for provide/require statements
     * to discern dependencies, build dependency files (see deps.js), etc.
     * @see goog.require
     * @param {string} name Namespace provided by this file in the form
     *     "goog.package.part".
     */
    goog.provide = function(name) {
      if (!COMPILED) {
        // Ensure that the same namespace isn't provided twice. This is intended
        // to teach new developers that 'goog.provide' is effectively a variable
        // declaration. And when JSCompiler transforms goog.provide into a real
        // variable declaration, the compiled JS should work the same as the raw
        // JS--even when the raw JS uses goog.provide incorrectly.
        if (goog.isProvided_(name)) {
          throw Error('Namespace "' + name + '" already declared.');
        }
        delete goog.implicitNamespaces_[name];
    
        var namespace = name;
        while ((namespace = namespace.substring(0, namespace.lastIndexOf('.')))) {
          if (goog.getObjectByName(namespace)) {
            break;
          }
          goog.implicitNamespaces_[namespace] = true;
        }
      }
    
      goog.exportPath_(name);
    };
    
    
    /**
     * Marks that the current file should only be used for testing, and never for
     * live code in production.
     *
     * In the case of unit tests, the message may optionally be an exact namespace
     * for the test (e.g. 'goog.stringTest'). The linter will then ignore the extra
     * provide (if not explicitly defined in the code).
     *
     * @param {string=} opt_message Optional message to add to the error that's
     *     raised when used in production code.
     */
    goog.setTestOnly = function(opt_message) {
      if (COMPILED && !goog.DEBUG) {
        opt_message = opt_message || '';
        throw Error('Importing test-only code into non-debug environment' +
                    opt_message ? ': ' + opt_message : '.');
      }
    };
    
    
    /**
     * Forward declares a symbol. This is an indication to the compiler that the
     * symbol may be used in the source yet is not required and may not be provided
     * in compilation.
     *
     * The most common usage of forward declaration is code that takes a type as a
     * function parameter but does not need to require it. By forward declaring
     * instead of requiring, no hard dependency is made, and (if not required
     * elsewhere) the namespace may never be required and thus, not be pulled
     * into the JavaScript binary. If it is required elsewhere, it will be type
     * checked as normal.
     *
     *
     * @param {string} name The namespace to forward declare in the form of
     *     "goog.package.part".
     */
    goog.forwardDeclare = function(name) {};
    
    
    if (!COMPILED) {
    
      /**
       * Check if the given name has been goog.provided. This will return false for
       * names that are available only as implicit namespaces.
       * @param {string} name name of the object to look for.
       * @return {boolean} Whether the name has been provided.
       * @private
       */
      goog.isProvided_ = function(name) {
        return !goog.implicitNamespaces_[name] &&
            goog.isDefAndNotNull(goog.getObjectByName(name));
      };
    
      /**
       * Namespaces implicitly defined by goog.provide. For example,
       * goog.provide('goog.events.Event') implicitly declares that 'goog' and
       * 'goog.events' must be namespaces.
       *
       * @type {Object}
       * @private
       */
      goog.implicitNamespaces_ = {};
    }
    
    
    /**
     * Returns an object based on its fully qualified external name.  The object
     * is not found if null or undefined.  If you are using a compilation pass that
     * renames property names beware that using this function will not find renamed
     * properties.
     *
     * @param {string} name The fully qualified name.
     * @param {Object=} opt_obj The object within which to look; default is
     *     |goog.global|.
     * @return {?} The value (object or primitive) or, if not found, null.
     */
    goog.getObjectByName = function(name, opt_obj) {
      var parts = name.split('.');
      var cur = opt_obj || goog.global;
      for (var part; part = parts.shift(); ) {
        if (goog.isDefAndNotNull(cur[part])) {
          cur = cur[part];
        } else {
          return null;
        }
      }
      return cur;
    };
    
    
    /**
     * Globalizes a whole namespace, such as goog or goog.lang.
     *
     * @param {Object} obj The namespace to globalize.
     * @param {Object=} opt_global The object to add the properties to.
     * @deprecated Properties may be explicitly exported to the global scope, but
     *     this should no longer be done in bulk.
     */
    goog.globalize = function(obj, opt_global) {
      var global = opt_global || goog.global;
      for (var x in obj) {
        global[x] = obj[x];
      }
    };
    
    
    /**
     * Adds a dependency from a file to the files it requires.
     * @param {string} relPath The path to the js file.
     * @param {Array} provides An array of strings with the names of the objects
     *                         this file provides.
     * @param {Array} requires An array of strings with the names of the objects
     *                         this file requires.
     */
    goog.addDependency = function(relPath, provides, requires) {
      if (goog.DEPENDENCIES_ENABLED) {
        var provide, require;
        var path = relPath.replace(/\\/g, '/');
        var deps = goog.dependencies_;
        for (var i = 0; provide = provides[i]; i++) {
          deps.nameToPath[provide] = path;
          if (!(path in deps.pathToNames)) {
            deps.pathToNames[path] = {};
          }
          deps.pathToNames[path][provide] = true;
        }
        for (var j = 0; require = requires[j]; j++) {
          if (!(path in deps.requires)) {
            deps.requires[path] = {};
          }
          deps.requires[path][require] = true;
        }
      }
    };
    
    
    
    
    // NOTE(nnaze): The debug DOM loader was included in base.js as an original way
    // to do "debug-mode" development.  The dependency system can sometimes be
    // confusing, as can the debug DOM loader's asynchronous nature.
    //
    // With the DOM loader, a call to goog.require() is not blocking -- the script
    // will not load until some point after the current script.  If a namespace is
    // needed at runtime, it needs to be defined in a previous script, or loaded via
    // require() with its registered dependencies.
    // User-defined namespaces may need their own deps file.  See http://go/js_deps,
    // http://go/genjsdeps, or, externally, DepsWriter.
    // http://code.google.com/closure/library/docs/depswriter.html
    //
    // Because of legacy clients, the DOM loader can't be easily removed from
    // base.js.  Work is being done to make it disableable or replaceable for
    // different environments (DOM-less JavaScript interpreters like Rhino or V8,
    // for example). See bootstrap/ for more information.
    
    
    /**
     * @define {boolean} Whether to enable the debug loader.
     *
     * If enabled, a call to goog.require() will attempt to load the namespace by
     * appending a script tag to the DOM (if the namespace has been registered).
     *
     * If disabled, goog.require() will simply assert that the namespace has been
     * provided (and depend on the fact that some outside tool correctly ordered
     * the script).
     */
    goog.define('goog.ENABLE_DEBUG_LOADER', true);
    
    
    /**
     * Implements a system for the dynamic resolution of dependencies that works in
     * parallel with the BUILD system. Note that all calls to goog.require will be
     * stripped by the JSCompiler when the --closure_pass option is used.
     * @see goog.provide
     * @param {string} name Namespace to include (as was given in goog.provide()) in
     *     the form "goog.package.part".
     */
    goog.require = function(name) {
    
      // If the object already exists we do not need do do anything.
      // TODO(arv): If we start to support require based on file name this has to
      //            change.
      // TODO(arv): If we allow goog.foo.* this has to change.
      // TODO(arv): If we implement dynamic load after page load we should probably
      //            not remove this code for the compiled output.
      if (!COMPILED) {
        if (goog.isProvided_(name)) {
          return;
        }
    
        if (goog.ENABLE_DEBUG_LOADER) {
          var path = goog.getPathFromDeps_(name);
          if (path) {
            goog.included_[path] = true;
            goog.writeScripts_();
            return;
          }
        }
    
        var errorMessage = 'goog.require could not find: ' + name;
        if (goog.global.console) {
          goog.global.console['error'](errorMessage);
        }
    
    
          throw Error(errorMessage);
    
      }
    };
    
    
    /**
     * Path for included scripts.
     * @type {string}
     */
    goog.basePath = '';
    
    
    /**
     * A hook for overriding the base path.
     * @type {string|undefined}
     */
    goog.global.CLOSURE_BASE_PATH;
    
    
    /**
     * Whether to write out Closure's deps file. By default, the deps are written.
     * @type {boolean|undefined}
     */
    goog.global.CLOSURE_NO_DEPS;
    
    
    /**
     * A function to import a single script. This is meant to be overridden when
     * Closure is being run in non-HTML contexts, such as web workers. It's defined
     * in the global scope so that it can be set before base.js is loaded, which
     * allows deps.js to be imported properly.
     *
     * The function is passed the script source, which is a relative URI. It should
     * return true if the script was imported, false otherwise.
     * @type {(function(string): boolean)|undefined}
     */
    goog.global.CLOSURE_IMPORT_SCRIPT;
    
    
    /**
     * Null function used for default values of callbacks, etc.
     * @return {void} Nothing.
     */
    goog.nullFunction = function() {};
    
    
    /**
     * The identity function. Returns its first argument.
     *
     * @param {*=} opt_returnValue The single value that will be returned.
     * @param {...*} var_args Optional trailing arguments. These are ignored.
     * @return {?} The first argument. We can't know the type -- just pass it along
     *      without type.
     * @deprecated Use goog.functions.identity instead.
     */
    goog.identityFunction = function(opt_returnValue, var_args) {
      return opt_returnValue;
    };
    
    
    /**
     * When defining a class Foo with an abstract method bar(), you can do:
     * Foo.prototype.bar = goog.abstractMethod
     *
     * Now if a subclass of Foo fails to override bar(), an error will be thrown
     * when bar() is invoked.
     *
     * Note: This does not take the name of the function to override as an argument
     * because that would make it more difficult to obfuscate our JavaScript code.
     *
     * @type {!Function}
     * @throws {Error} when invoked to indicate the method should be overridden.
     */
    goog.abstractMethod = function() {
      throw Error('unimplemented abstract method');
    };
    
    
    /**
     * Adds a {@code getInstance} static method that always returns the same
     * instance object.
     * @param {!Function} ctor The constructor for the class to add the static
     *     method to.
     */
    goog.addSingletonGetter = function(ctor) {
      ctor.getInstance = function() {
        if (ctor.instance_) {
          return ctor.instance_;
        }
        if (goog.DEBUG) {
          // NOTE: JSCompiler can't optimize away Array#push.
          goog.instantiatedSingletons_[goog.instantiatedSingletons_.length] = ctor;
        }
        return ctor.instance_ = new ctor;
      };
    };
    
    
    /**
     * All singleton classes that have been instantiated, for testing. Don't read
     * it directly, use the {@code goog.testing.singleton} module. The compiler
     * removes this variable if unused.
     * @type {!Array.<!Function>}
     * @private
     */
    goog.instantiatedSingletons_ = [];
    
    
    /**
     * True if goog.dependencies_ is available.
     * @const {boolean}
     */
    goog.DEPENDENCIES_ENABLED = !COMPILED && goog.ENABLE_DEBUG_LOADER;
    
    
    if (goog.DEPENDENCIES_ENABLED) {
      /**
       * Object used to keep track of urls that have already been added. This record
       * allows the prevention of circular dependencies.
       * @type {Object}
       * @private
       */
      goog.included_ = {};
    
    
      /**
       * This object is used to keep track of dependencies and other data that is
       * used for loading scripts.
       * @private
       * @type {Object}
       */
      goog.dependencies_ = {
        pathToNames: {}, // 1 to many
        nameToPath: {}, // 1 to 1
        requires: {}, // 1 to many
        // Used when resolving dependencies to prevent us from visiting file twice.
        visited: {},
        written: {} // Used to keep track of script files we have written.
      };
    
    
      /**
       * Tries to detect whether is in the context of an HTML document.
       * @return {boolean} True if it looks like HTML document.
       * @private
       */
      goog.inHtmlDocument_ = function() {
        var doc = goog.global.document;
        return typeof doc != 'undefined' &&
               'write' in doc;  // XULDocument misses write.
      };
    
    
      /**
       * Tries to detect the base path of base.js script that bootstraps Closure.
       * @private
       */
      goog.findBasePath_ = function() {
        if (goog.global.CLOSURE_BASE_PATH) {
          goog.basePath = goog.global.CLOSURE_BASE_PATH;
          return;
        } else if (!goog.inHtmlDocument_()) {
          return;
        }
        var doc = goog.global.document;
        var scripts = doc.getElementsByTagName('script');
        // Search backwards since the current script is in almost all cases the one
        // that has base.js.
        for (var i = scripts.length - 1; i >= 0; --i) {
          var src = scripts[i].src;
          var qmark = src.lastIndexOf('?');
          var l = qmark == -1 ? src.length : qmark;
          if (src.substr(l - 7, 7) == 'base.js') {
            goog.basePath = src.substr(0, l - 7);
            return;
          }
        }
      };
    
    
      /**
       * Imports a script if, and only if, that script hasn't already been imported.
       * (Must be called at execution time)
       * @param {string} src Script source.
       * @private
       */
      goog.importScript_ = function(src) {
        var importScript = goog.global.CLOSURE_IMPORT_SCRIPT ||
            goog.writeScriptTag_;
        if (!goog.dependencies_.written[src] && importScript(src)) {
          goog.dependencies_.written[src] = true;
        }
      };
    
    
      /**
       * The default implementation of the import function. Writes a script tag to
       * import the script.
       *
       * @param {string} src The script source.
       * @return {boolean} True if the script was imported, false otherwise.
       * @private
       */
      goog.writeScriptTag_ = function(src) {
        if (goog.inHtmlDocument_()) {
          var doc = goog.global.document;
    
          // If the user tries to require a new symbol after document load,
          // something has gone terribly wrong. Doing a document.write would
          // wipe out the page.
          if (doc.readyState == 'complete') {
            // Certain test frameworks load base.js multiple times, which tries
            // to write deps.js each time. If that happens, just fail silently.
            // These frameworks wipe the page between each load of base.js, so this
            // is OK.
            var isDeps = /\bdeps.js$/.test(src);
            if (isDeps) {
              return false;
            } else {
              throw Error('Cannot write "' + src + '" after document load');
            }
          }
    
          doc.write(
              '<script type="text/javascript" src="' + src + '"></' + 'script>');
          return true;
        } else {
          return false;
        }
      };
    
    
      /**
       * Resolves dependencies based on the dependencies added using addDependency
       * and calls importScript_ in the correct order.
       * @private
       */
      goog.writeScripts_ = function() {
        // The scripts we need to write this time.
        var scripts = [];
        var seenScript = {};
        var deps = goog.dependencies_;
    
        function visitNode(path) {
          if (path in deps.written) {
            return;
          }
    
          // We have already visited this one. We can get here if we have cyclic
          // dependencies.
          if (path in deps.visited) {
            if (!(path in seenScript)) {
              seenScript[path] = true;
              scripts.push(path);
            }
            return;
          }
    
          deps.visited[path] = true;
    
          if (path in deps.requires) {
            for (var requireName in deps.requires[path]) {
              // If the required name is defined, we assume that it was already
              // bootstrapped by other means.
              if (!goog.isProvided_(requireName)) {
                if (requireName in deps.nameToPath) {
                  visitNode(deps.nameToPath[requireName]);
                } else {
                  throw Error('Undefined nameToPath for ' + requireName);
                }
              }
            }
          }
    
          if (!(path in seenScript)) {
            seenScript[path] = true;
            scripts.push(path);
          }
        }
    
        for (var path in goog.included_) {
          if (!deps.written[path]) {
            visitNode(path);
          }
        }
    
        for (var i = 0; i < scripts.length; i++) {
          if (scripts[i]) {
            goog.importScript_(goog.basePath + scripts[i]);
          } else {
            throw Error('Undefined script input');
          }
        }
      };
    
    
      /**
       * Looks at the dependency rules and tries to determine the script file that
       * fulfills a particular rule.
       * @param {string} rule In the form goog.namespace.Class or project.script.
       * @return {?string} Url corresponding to the rule, or null.
       * @private
       */
      goog.getPathFromDeps_ = function(rule) {
        if (rule in goog.dependencies_.nameToPath) {
          return goog.dependencies_.nameToPath[rule];
        } else {
          return null;
        }
      };
    
      goog.findBasePath_();
    
      // Allow projects to manage the deps files themselves.
      if (!goog.global.CLOSURE_NO_DEPS) {
        goog.importScript_(goog.basePath + 'deps.js');
      }
    }
    
    
    
    //==============================================================================
    // Language Enhancements
    //==============================================================================
    
    
    /**
     * This is a "fixed" version of the typeof operator.  It differs from the typeof
     * operator in such a way that null returns 'null' and arrays return 'array'.
     * @param {*} value The value to get the type of.
     * @return {string} The name of the type.
     */
    goog.typeOf = function(value) {
      var s = typeof value;
      if (s == 'object') {
        if (value) {
          // Check these first, so we can avoid calling Object.prototype.toString if
          // possible.
          //
          // IE improperly marshals tyepof across execution contexts, but a
          // cross-context object will still return false for "instanceof Object".
          if (value instanceof Array) {
            return 'array';
          } else if (value instanceof Object) {
            return s;
          }
    
          // HACK: In order to use an Object prototype method on the arbitrary
          //   value, the compiler requires the value be cast to type Object,
          //   even though the ECMA spec explicitly allows it.
          var className = Object.prototype.toString.call(
              /** @type {Object} */ (value));
          // In Firefox 3.6, attempting to access iframe window objects' length
          // property throws an NS_ERROR_FAILURE, so we need to special-case it
          // here.
          if (className == '[object Window]') {
            return 'object';
          }
    
          // We cannot always use constructor == Array or instanceof Array because
          // different frames have different Array objects. In IE6, if the iframe
          // where the array was created is destroyed, the array loses its
          // prototype. Then dereferencing val.splice here throws an exception, so
          // we can't use goog.isFunction. Calling typeof directly returns 'unknown'
          // so that will work. In this case, this function will return false and
          // most array functions will still work because the array is still
          // array-like (supports length and []) even though it has lost its
          // prototype.
          // Mark Miller noticed that Object.prototype.toString
          // allows access to the unforgeable [[Class]] property.
          //  15.2.4.2 Object.prototype.toString ( )
          //  When the toString method is called, the following steps are taken:
          //      1. Get the [[Class]] property of this object.
          //      2. Compute a string value by concatenating the three strings
          //         "[object ", Result(1), and "]".
          //      3. Return Result(2).
          // and this behavior survives the destruction of the execution context.
          if ((className == '[object Array]' ||
               // In IE all non value types are wrapped as objects across window
               // boundaries (not iframe though) so we have to do object detection
               // for this edge case.
               typeof value.length == 'number' &&
               typeof value.splice != 'undefined' &&
               typeof value.propertyIsEnumerable != 'undefined' &&
               !value.propertyIsEnumerable('splice')
    
              )) {
            return 'array';
          }
          // HACK: There is still an array case that fails.
          //     function ArrayImpostor() {}
          //     ArrayImpostor.prototype = [];
          //     var impostor = new ArrayImpostor;
          // this can be fixed by getting rid of the fast path
          // (value instanceof Array) and solely relying on
          // (value && Object.prototype.toString.vall(value) === '[object Array]')
          // but that would require many more function calls and is not warranted
          // unless closure code is receiving objects from untrusted sources.
    
          // IE in cross-window calls does not correctly marshal the function type
          // (it appears just as an object) so we cannot use just typeof val ==
          // 'function'. However, if the object has a call property, it is a
          // function.
          if ((className == '[object Function]' ||
              typeof value.call != 'undefined' &&
              typeof value.propertyIsEnumerable != 'undefined' &&
              !value.propertyIsEnumerable('call'))) {
            return 'function';
          }
    
        } else {
          return 'null';
        }
    
      } else if (s == 'function' && typeof value.call == 'undefined') {
        // In Safari typeof nodeList returns 'function', and on Firefox typeof
        // behaves similarly for HTML{Applet,Embed,Object}, Elements and RegExps. We
        // would like to return object for those and we can detect an invalid
        // function by making sure that the function object has a call method.
        return 'object';
      }
      return s;
    };
    
    
    /**
     * Returns true if the specified value is not undefined.
     * WARNING: Do not use this to test if an object has a property. Use the in
     * operator instead.  Additionally, this function assumes that the global
     * undefined variable has not been redefined.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is defined.
     */
    goog.isDef = function(val) {
      return val !== undefined;
    };
    
    
    /**
     * Returns true if the specified value is null.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is null.
     */
    goog.isNull = function(val) {
      return val === null;
    };
    
    
    /**
     * Returns true if the specified value is defined and not null.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is defined and not null.
     */
    goog.isDefAndNotNull = function(val) {
      // Note that undefined == null.
      return val != null;
    };
    
    
    /**
     * Returns true if the specified value is an array.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is an array.
     */
    goog.isArray = function(val) {
      return goog.typeOf(val) == 'array';
    };
    
    
    /**
     * Returns true if the object looks like an array. To qualify as array like
     * the value needs to be either a NodeList or an object with a Number length
     * property.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is an array.
     */
    goog.isArrayLike = function(val) {
      var type = goog.typeOf(val);
      return type == 'array' || type == 'object' && typeof val.length == 'number';
    };
    
    
    /**
     * Returns true if the object looks like a Date. To qualify as Date-like the
     * value needs to be an object and have a getFullYear() function.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is a like a Date.
     */
    goog.isDateLike = function(val) {
      return goog.isObject(val) && typeof val.getFullYear == 'function';
    };
    
    
    /**
     * Returns true if the specified value is a string.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is a string.
     */
    goog.isString = function(val) {
      return typeof val == 'string';
    };
    
    
    /**
     * Returns true if the specified value is a boolean.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is boolean.
     */
    goog.isBoolean = function(val) {
      return typeof val == 'boolean';
    };
    
    
    /**
     * Returns true if the specified value is a number.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is a number.
     */
    goog.isNumber = function(val) {
      return typeof val == 'number';
    };
    
    
    /**
     * Returns true if the specified value is a function.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is a function.
     */
    goog.isFunction = function(val) {
      return goog.typeOf(val) == 'function';
    };
    
    
    /**
     * Returns true if the specified value is an object.  This includes arrays and
     * functions.
     * @param {?} val Variable to test.
     * @return {boolean} Whether variable is an object.
     */
    goog.isObject = function(val) {
      var type = typeof val;
      return type == 'object' && val != null || type == 'function';
      // return Object(val) === val also works, but is slower, especially if val is
      // not an object.
    };
    
    
    /**
     * Gets a unique ID for an object. This mutates the object so that further calls
     * with the same object as a parameter returns the same value. The unique ID is
     * guaranteed to be unique across the current session amongst objects that are
     * passed into {@code getUid}. There is no guarantee that the ID is unique or
     * consistent across sessions. It is unsafe to generate unique ID for function
     * prototypes.
     *
     * @param {Object} obj The object to get the unique ID for.
     * @return {number} The unique ID for the object.
     */
    goog.getUid = function(obj) {
      // TODO(arv): Make the type stricter, do not accept null.
    
      // In Opera window.hasOwnProperty exists but always returns false so we avoid
      // using it. As a consequence the unique ID generated for BaseClass.prototype
      // and SubClass.prototype will be the same.
      return obj[goog.UID_PROPERTY_] ||
          (obj[goog.UID_PROPERTY_] = ++goog.uidCounter_);
    };
    
    
    /**
     * Whether the given object is alreay assigned a unique ID.
     *
     * This does not modify the object.
     *
     * @param {Object} obj The object to check.
     * @return {boolean} Whether there an assigned unique id for the object.
     */
    goog.hasUid = function(obj) {
      return !!obj[goog.UID_PROPERTY_];
    };
    
    
    /**
     * Removes the unique ID from an object. This is useful if the object was
     * previously mutated using {@code goog.getUid} in which case the mutation is
     * undone.
     * @param {Object} obj The object to remove the unique ID field from.
     */
    goog.removeUid = function(obj) {
      // TODO(arv): Make the type stricter, do not accept null.
    
      // In IE, DOM nodes are not instances of Object and throw an exception if we
      // try to delete.  Instead we try to use removeAttribute.
      if ('removeAttribute' in obj) {
        obj.removeAttribute(goog.UID_PROPERTY_);
      }
      /** @preserveTry */
      try {
        delete obj[goog.UID_PROPERTY_];
      } catch (ex) {
      }
    };
    
    
    /**
     * Name for unique ID property. Initialized in a way to help avoid collisions
     * with other closure JavaScript on the same page.
     * @type {string}
     * @private
     */
    goog.UID_PROPERTY_ = 'closure_uid_' + ((Math.random() * 1e9) >>> 0);
    
    
    /**
     * Counter for UID.
     * @type {number}
     * @private
     */
    goog.uidCounter_ = 0;
    
    
    /**
     * Adds a hash code field to an object. The hash code is unique for the
     * given object.
     * @param {Object} obj The object to get the hash code for.
     * @return {number} The hash code for the object.
     * @deprecated Use goog.getUid instead.
     */
    goog.getHashCode = goog.getUid;
    
    
    /**
     * Removes the hash code field from an object.
     * @param {Object} obj The object to remove the field from.
     * @deprecated Use goog.removeUid instead.
     */
    goog.removeHashCode = goog.removeUid;
    
    
    /**
     * Clones a value. The input may be an Object, Array, or basic type. Objects and
     * arrays will be cloned recursively.
     *
     * WARNINGS:
     * <code>goog.cloneObject</code> does not detect reference loops. Objects that
     * refer to themselves will cause infinite recursion.
     *
     * <code>goog.cloneObject</code> is unaware of unique identifiers, and copies
     * UIDs created by <code>getUid</code> into cloned results.
     *
     * @param {*} obj The value to clone.
     * @return {*} A clone of the input value.
     * @deprecated goog.cloneObject is unsafe. Prefer the goog.object methods.
     */
    goog.cloneObject = function(obj) {
      var type = goog.typeOf(obj);
      if (type == 'object' || type == 'array') {
        if (obj.clone) {
          return obj.clone();
        }
        var clone = type == 'array' ? [] : {};
        for (var key in obj) {
          clone[key] = goog.cloneObject(obj[key]);
        }
        return clone;
      }
    
      return obj;
    };
    
    
    /**
     * A native implementation of goog.bind.
     * @param {Function} fn A function to partially apply.
     * @param {Object|undefined} selfObj Specifies the object which this should
     *     point to when the function is run.
     * @param {...*} var_args Additional arguments that are partially applied to the
     *     function.
     * @return {!Function} A partially-applied form of the function bind() was
     *     invoked as a method of.
     * @private
     * @suppress {deprecated} The compiler thinks that Function.prototype.bind is
     *     deprecated because some people have declared a pure-JS version.
     *     Only the pure-JS version is truly deprecated.
     */
    goog.bindNative_ = function(fn, selfObj, var_args) {
      return /** @type {!Function} */ (fn.call.apply(fn.bind, arguments));
    };
    
    
    /**
     * A pure-JS implementation of goog.bind.
     * @param {Function} fn A function to partially apply.
     * @param {Object|undefined} selfObj Specifies the object which this should
     *     point to when the function is run.
     * @param {...*} var_args Additional arguments that are partially applied to the
     *     function.
     * @return {!Function} A partially-applied form of the function bind() was
     *     invoked as a method of.
     * @private
     */
    goog.bindJs_ = function(fn, selfObj, var_args) {
      if (!fn) {
        throw new Error();
      }
    
      if (arguments.length > 2) {
        var boundArgs = Array.prototype.slice.call(arguments, 2);
        return function() {
          // Prepend the bound arguments to the current arguments.
          var newArgs = Array.prototype.slice.call(arguments);
          Array.prototype.unshift.apply(newArgs, boundArgs);
          return fn.apply(selfObj, newArgs);
        };
    
      } else {
        return function() {
          return fn.apply(selfObj, arguments);
        };
      }
    };
    
    
    /**
     * Partially applies this function to a particular 'this object' and zero or
     * more arguments. The result is a new function with some arguments of the first
     * function pre-filled and the value of this 'pre-specified'.
     *
     * Remaining arguments specified at call-time are appended to the pre-specified
     * ones.
     *
     * Also see: {@link #partial}.
     *
     * Usage:
     * <pre>var barMethBound = bind(myFunction, myObj, 'arg1', 'arg2');
     * barMethBound('arg3', 'arg4');</pre>
     *
     * @param {?function(this:T, ...)} fn A function to partially apply.
     * @param {T} selfObj Specifies the object which this should point to when the
     *     function is run.
     * @param {...*} var_args Additional arguments that are partially applied to the
     *     function.
     * @return {!Function} A partially-applied form of the function bind() was
     *     invoked as a method of.
     * @template T
     * @suppress {deprecated} See above.
     */
    goog.bind = function(fn, selfObj, var_args) {
      // TODO(nicksantos): narrow the type signature.
      if (Function.prototype.bind &&
          // NOTE(nicksantos): Somebody pulled base.js into the default Chrome
          // extension environment. This means that for Chrome extensions, they get
          // the implementation of Function.prototype.bind that calls goog.bind
          // instead of the native one. Even worse, we don't want to introduce a
          // circular dependency between goog.bind and Function.prototype.bind, so
          // we have to hack this to make sure it works correctly.
          Function.prototype.bind.toString().indexOf('native code') != -1) {
        goog.bind = goog.bindNative_;
      } else {
        goog.bind = goog.bindJs_;
      }
      return goog.bind.apply(null, arguments);
    };
    
    
    /**
     * Like bind(), except that a 'this object' is not required. Useful when the
     * target function is already bound.
     *
     * Usage:
     * var g = partial(f, arg1, arg2);
     * g(arg3, arg4);
     *
     * @param {Function} fn A function to partially apply.
     * @param {...*} var_args Additional arguments that are partially applied to fn.
     * @return {!Function} A partially-applied form of the function bind() was
     *     invoked as a method of.
     */
    goog.partial = function(fn, var_args) {
      var args = Array.prototype.slice.call(arguments, 1);
      return function() {
        // Clone the array (with slice()) and append additional arguments
        // to the existing arguments.
        var newArgs = args.slice();
        newArgs.push.apply(newArgs, arguments);
        return fn.apply(this, newArgs);
      };
    };
    
    
    /**
     * Copies all the members of a source object to a target object. This method
     * does not work on all browsers for all objects that contain keys such as
     * toString or hasOwnProperty. Use goog.object.extend for this purpose.
     * @param {Object} target Target.
     * @param {Object} source Source.
     */
    goog.mixin = function(target, source) {
      for (var x in source) {
        target[x] = source[x];
      }
    
      // For IE7 or lower, the for-in-loop does not contain any properties that are
      // not enumerable on the prototype object (for example, isPrototypeOf from
      // Object.prototype) but also it will not include 'replace' on objects that
      // extend String and change 'replace' (not that it is common for anyone to
      // extend anything except Object).
    };
    
    
    /**
     * @return {number} An integer value representing the number of milliseconds
     *     between midnight, January 1, 1970 and the current time.
     */
    goog.now = (goog.TRUSTED_SITE && Date.now) || (function() {
      // Unary plus operator converts its operand to a number which in the case of
      // a date is done by calling getTime().
      return +new Date();
    });
    
    
    /**
     * Evals JavaScript in the global scope.  In IE this uses execScript, other
     * browsers use goog.global.eval. If goog.global.eval does not evaluate in the
     * global scope (for example, in Safari), appends a script tag instead.
     * Throws an exception if neither execScript or eval is defined.
     * @param {string} script JavaScript string.
     */
    goog.globalEval = function(script) {
      if (goog.global.execScript) {
        goog.global.execScript(script, 'JavaScript');
      } else if (goog.global.eval) {
        // Test to see if eval works
        if (goog.evalWorksForGlobals_ == null) {
          goog.global.eval('var _et_ = 1;');
          if (typeof goog.global['_et_'] != 'undefined') {
            delete goog.global['_et_'];
            goog.evalWorksForGlobals_ = true;
          } else {
            goog.evalWorksForGlobals_ = false;
          }
        }
    
        if (goog.evalWorksForGlobals_) {
          goog.global.eval(script);
        } else {
          var doc = goog.global.document;
          var scriptElt = doc.createElement('script');
          scriptElt.type = 'text/javascript';
          scriptElt.defer = false;
          // Note(user): can't use .innerHTML since "t('<test>')" will fail and
          // .text doesn't work in Safari 2.  Therefore we append a text node.
          scriptElt.appendChild(doc.createTextNode(script));
          doc.body.appendChild(scriptElt);
          doc.body.removeChild(scriptElt);
        }
      } else {
        throw Error('goog.globalEval not available');
      }
    };
    
    
    /**
     * Indicates whether or not we can call 'eval' directly to eval code in the
     * global scope. Set to a Boolean by the first call to goog.globalEval (which
     * empirically tests whether eval works for globals). @see goog.globalEval
     * @type {?boolean}
     * @private
     */
    goog.evalWorksForGlobals_ = null;
    
    
    /**
     * Optional map of CSS class names to obfuscated names used with
     * goog.getCssName().
     * @type {Object|undefined}
     * @private
     * @see goog.setCssNameMapping
     */
    goog.cssNameMapping_;
    
    
    /**
     * Optional obfuscation style for CSS class names. Should be set to either
     * 'BY_WHOLE' or 'BY_PART' if defined.
     * @type {string|undefined}
     * @private
     * @see goog.setCssNameMapping
     */
    goog.cssNameMappingStyle_;
    
    
    /**
     * Handles strings that are intended to be used as CSS class names.
     *
     * This function works in tandem with @see goog.setCssNameMapping.
     *
     * Without any mapping set, the arguments are simple joined with a hyphen and
     * passed through unaltered.
     *
     * When there is a mapping, there are two possible styles in which these
     * mappings are used. In the BY_PART style, each part (i.e. in between hyphens)
     * of the passed in css name is rewritten according to the map. In the BY_WHOLE
     * style, the full css name is looked up in the map directly. If a rewrite is
     * not specified by the map, the compiler will output a warning.
     *
     * When the mapping is passed to the compiler, it will replace calls to
     * goog.getCssName with the strings from the mapping, e.g.
     *     var x = goog.getCssName('foo');
     *     var y = goog.getCssName(this.baseClass, 'active');
     *  becomes:
     *     var x= 'foo';
     *     var y = this.baseClass + '-active';
     *
     * If one argument is passed it will be processed, if two are passed only the
     * modifier will be processed, as it is assumed the first argument was generated
     * as a result of calling goog.getCssName.
     *
     * @param {string} className The class name.
     * @param {string=} opt_modifier A modifier to be appended to the class name.
     * @return {string} The class name or the concatenation of the class name and
     *     the modifier.
     */
    goog.getCssName = function(className, opt_modifier) {
      var getMapping = function(cssName) {
        return goog.cssNameMapping_[cssName] || cssName;
      };
    
      var renameByParts = function(cssName) {
        // Remap all the parts individually.
        var parts = cssName.split('-');
        var mapped = [];
        for (var i = 0; i < parts.length; i++) {
          mapped.push(getMapping(parts[i]));
        }
        return mapped.join('-');
      };
    
      var rename;
      if (goog.cssNameMapping_) {
        rename = goog.cssNameMappingStyle_ == 'BY_WHOLE' ?
            getMapping : renameByParts;
      } else {
        rename = function(a) {
          return a;
        };
      }
    
      if (opt_modifier) {
        return className + '-' + rename(opt_modifier);
      } else {
        return rename(className);
      }
    };
    
    
    /**
     * Sets the map to check when returning a value from goog.getCssName(). Example:
     * <pre>
     * goog.setCssNameMapping({
     *   "goog": "a",
     *   "disabled": "b",
     * });
     *
     * var x = goog.getCssName('goog');
     * // The following evaluates to: "a a-b".
     * goog.getCssName('goog') + ' ' + goog.getCssName(x, 'disabled')
     * </pre>
     * When declared as a map of string literals to string literals, the JSCompiler
     * will replace all calls to goog.getCssName() using the supplied map if the
     * --closure_pass flag is set.
     *
     * @param {!Object} mapping A map of strings to strings where keys are possible
     *     arguments to goog.getCssName() and values are the corresponding values
     *     that should be returned.
     * @param {string=} opt_style The style of css name mapping. There are two valid
     *     options: 'BY_PART', and 'BY_WHOLE'.
     * @see goog.getCssName for a description.
     */
    goog.setCssNameMapping = function(mapping, opt_style) {
      goog.cssNameMapping_ = mapping;
      goog.cssNameMappingStyle_ = opt_style;
    };
    
    
    /**
     * To use CSS renaming in compiled mode, one of the input files should have a
     * call to goog.setCssNameMapping() with an object literal that the JSCompiler
     * can extract and use to replace all calls to goog.getCssName(). In uncompiled
     * mode, JavaScript code should be loaded before this base.js file that declares
     * a global variable, CLOSURE_CSS_NAME_MAPPING, which is used below. This is
     * to ensure that the mapping is loaded before any calls to goog.getCssName()
     * are made in uncompiled mode.
     *
     * A hook for overriding the CSS name mapping.
     * @type {Object|undefined}
     */
    goog.global.CLOSURE_CSS_NAME_MAPPING;
    
    
    if (!COMPILED && goog.global.CLOSURE_CSS_NAME_MAPPING) {
      // This does not call goog.setCssNameMapping() because the JSCompiler
      // requires that goog.setCssNameMapping() be called with an object literal.
      goog.cssNameMapping_ = goog.global.CLOSURE_CSS_NAME_MAPPING;
    }
    
    
    /**
     * Gets a localized message.
     *
     * This function is a compiler primitive. If you give the compiler a localized
     * message bundle, it will replace the string at compile-time with a localized
     * version, and expand goog.getMsg call to a concatenated string.
     *
     * Messages must be initialized in the form:
     * <code>
     * var MSG_NAME = goog.getMsg('Hello {$placeholder}', {'placeholder': 'world'});
     * </code>
     *
     * @param {string} str Translatable string, places holders in the form {$foo}.
     * @param {Object=} opt_values Map of place holder name to value.
     * @return {string} message with placeholders filled.
     */
    goog.getMsg = function(str, opt_values) {
      var values = opt_values || {};
      for (var key in values) {
        var value = ('' + values[key]).replace(/\$/g, '$$$$');
        str = str.replace(new RegExp('\\{\\$' + key + '\\}', 'gi'), value);
      }
      return str;
    };
    
    
    /**
     * Gets a localized message. If the message does not have a translation, gives a
     * fallback message.
     *
     * This is useful when introducing a new message that has not yet been
     * translated into all languages.
     *
     * This function is a compiler primitive. Must be used in the form:
     * <code>var x = goog.getMsgWithFallback(MSG_A, MSG_B);</code>
     * where MSG_A and MSG_B were initialized with goog.getMsg.
     *
     * @param {string} a The preferred message.
     * @param {string} b The fallback message.
     * @return {string} The best translated message.
     */
    goog.getMsgWithFallback = function(a, b) {
      return a;
    };
    
    
    /**
     * Exposes an unobfuscated global namespace path for the given object.
     * Note that fields of the exported object *will* be obfuscated, unless they are
     * exported in turn via this function or goog.exportProperty.
     *
     * Also handy for making public items that are defined in anonymous closures.
     *
     * ex. goog.exportSymbol('public.path.Foo', Foo);
     *
     * ex. goog.exportSymbol('public.path.Foo.staticFunction', Foo.staticFunction);
     *     public.path.Foo.staticFunction();
     *
     * ex. goog.exportSymbol('public.path.Foo.prototype.myMethod',
     *                       Foo.prototype.myMethod);
     *     new public.path.Foo().myMethod();
     *
     * @param {string} publicPath Unobfuscated name to export.
     * @param {*} object Object the name should point to.
     * @param {Object=} opt_objectToExportTo The object to add the path to; default
     *     is goog.global.
     */
    goog.exportSymbol = function(publicPath, object, opt_objectToExportTo) {
      goog.exportPath_(publicPath, object, opt_objectToExportTo);
    };
    
    
    /**
     * Exports a property unobfuscated into the object's namespace.
     * ex. goog.exportProperty(Foo, 'staticFunction', Foo.staticFunction);
     * ex. goog.exportProperty(Foo.prototype, 'myMethod', Foo.prototype.myMethod);
     * @param {Object} object Object whose static property is being exported.
     * @param {string} publicName Unobfuscated name to export.
     * @param {*} symbol Object the name should point to.
     */
    goog.exportProperty = function(object, publicName, symbol) {
      object[publicName] = symbol;
    };
    
    
    /**
     * Inherit the prototype methods from one constructor into another.
     *
     * Usage:
     * <pre>
     * function ParentClass(a, b) { }
     * ParentClass.prototype.foo = function(a) { }
     *
     * function ChildClass(a, b, c) {
     *   goog.base(this, a, b);
     * }
     * goog.inherits(ChildClass, ParentClass);
     *
     * var child = new ChildClass('a', 'b', 'see');
     * child.foo(); // This works.
     * </pre>
     *
     * In addition, a superclass' implementation of a method can be invoked as
     * follows:
     *
     * <pre>
     * ChildClass.prototype.foo = function(a) {
     *   ChildClass.superClass_.foo.call(this, a);
     *   // Other code here.
     * };
     * </pre>
     *
     * @param {Function} childCtor Child class.
     * @param {Function} parentCtor Parent class.
     */
    goog.inherits = function(childCtor, parentCtor) {
      /** @constructor */
      function tempCtor() {};
      tempCtor.prototype = parentCtor.prototype;
      childCtor.superClass_ = parentCtor.prototype;
      childCtor.prototype = new tempCtor();
      /** @override */
      childCtor.prototype.constructor = childCtor;
    
      /**
       * Calls superclass constructor/method.
       *
       * This function is only available if you use goog.inherits to
       * express inheritance relationships between classes.
       *
       * NOTE: This is a replacement for goog.base and for superClass_
       * property defined in childCtor.
       *
       * @param {!Object} me Should always be "this".
       * @param {string} methodName The method name to call. Calling
       *     superclass constructor can be done with the special string
       *     'constructor'.
       * @param {...*} var_args The arguments to pass to superclass
       *     method/constructor.
       * @return {*} The return value of the superclass method/constructor.
       */
      childCtor.base = function(me, methodName, var_args) {
        var args = Array.prototype.slice.call(arguments, 2);
        return parentCtor.prototype[methodName].apply(me, args);
      };
    };
    
    
    /**
     * Call up to the superclass.
     *
     * If this is called from a constructor, then this calls the superclass
     * constructor with arguments 1-N.
     *
     * If this is called from a prototype method, then you must pass the name of the
     * method as the second argument to this function. If you do not, you will get a
     * runtime error. This calls the superclass' method with arguments 2-N.
     *
     * This function only works if you use goog.inherits to express inheritance
     * relationships between your classes.
     *
     * This function is a compiler primitive. At compile-time, the compiler will do
     * macro expansion to remove a lot of the extra overhead that this function
     * introduces. The compiler will also enforce a lot of the assumptions that this
     * function makes, and treat it as a compiler error if you break them.
     *
     * @param {!Object} me Should always be "this".
     * @param {*=} opt_methodName The method name if calling a super method.
     * @param {...*} var_args The rest of the arguments.
     * @return {*} The return value of the superclass method.
     * @suppress {es5Strict} This method can not be used in strict mode, but
     *     all Closure Library consumers must depend on this file.
     */
    goog.base = function(me, opt_methodName, var_args) {
      var caller = arguments.callee.caller;
    
      if (goog.STRICT_MODE_COMPATIBLE || (goog.DEBUG && !caller)) {
        throw Error('arguments.caller not defined.  goog.base() cannot be used ' +
                    'with strict mode code. See ' +
                    'http://www.ecma-international.org/ecma-262/5.1/#sec-C');
      }
    
      if (caller.superClass_) {
        // This is a constructor. Call the superclass constructor.
        return caller.superClass_.constructor.apply(
            me, Array.prototype.slice.call(arguments, 1));
      }
    
      var args = Array.prototype.slice.call(arguments, 2);
      var foundCaller = false;
      for (var ctor = me.constructor;
           ctor; ctor = ctor.superClass_ && ctor.superClass_.constructor) {
        if (ctor.prototype[opt_methodName] === caller) {
          foundCaller = true;
        } else if (foundCaller) {
          return ctor.prototype[opt_methodName].apply(me, args);
        }
      }
    
      // If we did not find the caller in the prototype chain, then one of two
      // things happened:
      // 1) The caller is an instance method.
      // 2) This method was not called by the right caller.
      if (me[opt_methodName] === caller) {
        return me.constructor.prototype[opt_methodName].apply(me, args);
      } else {
        throw Error(
            'goog.base called from a method of one name ' +
            'to a method of a different name');
      }
    };
    
    
    /**
     * Allow for aliasing within scope functions.  This function exists for
     * uncompiled code - in compiled code the calls will be inlined and the aliases
     * applied.  In uncompiled code the function is simply run since the aliases as
     * written are valid JavaScript.
     * @param {function()} fn Function to call.  This function can contain aliases
     *     to namespaces (e.g. "var dom = goog.dom") or classes
     *     (e.g. "var Timer = goog.Timer").
     */
    goog.scope = function(fn) {
      fn.call(goog.global);
    };
    
    goog.labs = goog.labs || {};
    goog.labs.classdef = goog.labs.classdef || {};
    
    
    /** @typedef {
         {constructor:!Function}|
         {constructor:!Function, statics:(Object|function(Function):void)}} */
    goog.labs.classdef.ClassDescriptor;
    
    
    /**
     * Creates a restricted form of a Closure "class":
     *   - from the compiler's perspective, the instance returned from the
     *     constructor is sealed (no new properties may be added).  This enables
     *     better type checking.
     *   - the compiler will rewrite this definition to a form that is optimal
     *     for type checking and optimization (initially this will be a more
     *     traditional form).
     *
     * @param {Function} superClass The superclass or null.
     * @param {goog.labs.classdef.ClassDescriptor} def
     *     An object literal describing the
     *     the class.  It may have the following properties:
     *     "constructor": the constructor function
     *     "statics": an object literal containing methods to add to the constructor
     *        as "static" methods or a function that will recieve the constructor
     *        function as its only parameter to which static properties can
     *        be added.
     *     all other properties are added to the prototype.
     * @return {!Function} The class constructor.
     */
    goog.labs.classdef.defineClass = function(superClass, def) {
      // TODO(johnlenz): consider making the superClass an optional parameter.
      var constructor = def.constructor;
      var statics = def.statics;
      // Wrap the constructor prior to setting up the prototype and static methods.
      if (!constructor || constructor == Object.prototype.constructor) {
        throw Error('constructor property is required.');
      }
    
      var cls = goog.labs.classdef.createSealingConstructor_(constructor);
      if (superClass) {
        goog.inherits(cls, superClass);
      }
    
      // Remove all the properties that should not be copied to the prototype.
      delete def.constructor;
      delete def.statics;
    
      goog.labs.classdef.applyProperties_(cls.prototype, def);
      if (statics != null) {
        if (statics instanceof Function) {
          statics(cls);
        } else {
          goog.labs.classdef.applyProperties_(cls, statics);
        }
      }
    
      return cls;
    };
    
    
    /**
     * @define {boolean} Whether the instances returned by
     * goog.labs.classdef.defineClass should be sealed when possible.
     */
    goog.labs.classdef.SEAL_CLASS_INSTANCES = false;
    
    
    /**
     * If goog.labs.classdef.SEAL_CLASS_INSTANCES is enabled and Object.seal is
     * defined, this function will wrap the constructor in a function that seals the
     * results of the provided constructor function.
     *
     * @param {!Function} ctr The constructor whose results maybe be sealed.
     * @return {!Function} The replacement constructor.
     * @private
     */
    goog.labs.classdef.createSealingConstructor_ = function(ctr) {
      if (goog.labs.classdef.SEAL_CLASS_INSTANCES &&
          Object.seal instanceof Function) {
        /** @this {*} */
        var wrappedCtr = function() {
          // Don't seal an instance of a subclass when it calls the constructor of
          // its super class as there is most likely still setup to do.
          var instance = ctr.apply(this, arguments) || this;
          if (this.constructor === wrappedCtr) {
            Object.seal(instance);
          }
          return instance;
        };
        return wrappedCtr;
      }
      return ctr;
    };
    
    
    // TODO(johnlenz): share these values with the goog.object
    /**
     * The names of the fields that are defined on Object.prototype.
     * @type {!Array.<string>}
     * @private
     * @const
     */
    goog.labs.classdef.OBJECT_PROTOTYPE_FIELDS_ = [
      'constructor',
      'hasOwnProperty',
      'isPrototypeOf',
      'propertyIsEnumerable',
      'toLocaleString',
      'toString',
      'valueOf'
    ];
    
    
    // TODO(johnlenz): share this function with the goog.object
    /**
     * @param {!Object} target The object to add properties to.
     * @param {!Object} source The object to copy properites from.
     * @private
     */
    goog.labs.classdef.applyProperties_ = function(target, source) {
      // TODO(johnlenz): update this to support ES5 getters/setters
    
      var key;
      for (key in source) {
        if (Object.prototype.hasOwnProperty.call(source, key)) {
          target[key] = source[key];
        }
      }
    
      // For IE the for-in-loop does not contain any properties that are not
      // enumerable on the prototype object (for example isPrototypeOf from
      // Object.prototype) and it will also not include 'replace' on objects that
      // extend String and change 'replace' (not that it is common for anyone to
      // extend anything except Object).
      for (var i = 0; i < goog.labs.classdef.OBJECT_PROTOTYPE_FIELDS_.length; i++) {
        key = goog.labs.classdef.OBJECT_PROTOTYPE_FIELDS_[i];
        if (Object.prototype.hasOwnProperty.call(source, key)) {
          target[key] = source[key];
        }
      }
    };

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Testing in
TestOps/sec
Closure
var Cls = goog.labs.classdef.defineClass(null, {
  constructor: function() {},
  methodA: function() { var a = 123; }
});  

var inst = new Cls();
inst.methodA();
ready
Native
var Cls = function() {};
Cls.prototype.methodA = function() { var a = 123; }

var inst = new Cls();
inst.methodA();
 
ready

Revisions

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  • Revision 1: published by Daniel Fielder on