Looping through array or obect for VS forEach

Benchmark created by Daniel on December 21, 2011

Description

Setup

// Object.keys shim.
    if(!Object.keys) Object.keys = function(o){  
     if (o !== Object(o))  
          throw new TypeError('Object.keys called on non-object');  
     var ret=[],p;  
     for(p in o) if(Object.prototype.hasOwnProperty.call(o,p)) ret.push(p);  
     return ret;  
    } 
    
    // Array.prototype.forEach shim.
    // Production steps of ECMA-262, Edition 5, 15.4.4.18
    // Reference: http://es5.github.com/#x15.4.4.18
    if ( !Array.prototype.forEach ) {
    
      Array.prototype.forEach = function( callback, thisArg ) {
    
        var T, k;
    
        if ( this == null ) {
          throw new TypeError( " this is null or not defined" );
        }
    
        // 1. Let O be the result of calling ToObject passing the |this| value as the argument.
        var O = Object(this);
    
        // 2. Let lenValue be the result of calling the Get internal method of O with the argument "length".
        // 3. Let len be ToUint32(lenValue).
        var len = O.length >>> 0; // Hack to convert O.length to a UInt32
    
        // 4. If IsCallable(callback) is false, throw a TypeError exception.
        // See: http://es5.github.com/#x9.11
        if ( {}.toString.call(callback) != "[object Function]" ) {
          throw new TypeError( callback + " is not a function" );
        }
    
        // 5. If thisArg was supplied, let T be thisArg; else let T be undefined.
        if ( thisArg ) {
          T = thisArg;
        }
    
        // 6. Let k be 0
        k = 0;
    
        // 7. Repeat, while k < len
        while( k < len ) {
    
          var kValue;
    
          // a. Let Pk be ToString(k).
          //   This is implicit for LHS operands of the in operator
          // b. Let kPresent be the result of calling the HasProperty internal method of O with argument Pk.
          //   This step can be combined with c
          // c. If kPresent is true, then
          if ( k in O ) {
    
            // i. Let kValue be the result of calling the Get internal method of O with argument Pk.
            kValue = O[ k ];
    
            // ii. Call the Call internal method of callback with T as the this value and
            // argument list containing kValue, k, and O.
            callback.call( T, kValue, k, O );
          }
          // d. Increase k by 1.
          k++;
        }
        // 8. return undefined
      };
    }
    
    // clone method A
    Object.prototype.cloneA = function() {
        var fn = function (o, cloner){
            if(o == null || typeof(o) != 'object') return o
            var no = new o.constructor()
            for(var key in o) no[key] = cloner(o[key], cloner) 
            return no;
        }
        return fn(this, fn)
    }
    // clone method B
    Object.prototype.cloneB = function() {
        var fn = function (o, cloner){
            if(o == null || typeof(o) != 'object') return o
            var no = new o.constructor()
            Object.keys(o).forEach(function(e){this[e] = cloner(o[e], cloner)},no) 
            return no;
        }
        return fn(this, fn)
    }
    
    var o = {a:'a',b:true,c:[1,2,3]}

Test runner

var oA = o.cloneA()
 

var oA = o.cloneB()

Revisions

You can edit these tests or add more tests to this page by appending /edit to the URL.

• Revision 1: published by Daniel on December 21, 2011