for vs forEach, including uncached length for worst-case (v203)

Revision 203 of this benchmark created on

Description

Is it faster to use the native forEach or just loop with for?

Inspired by Adrian Sutton's tests at: http://www.symphonious.net/2010/10/09/javascript-performance-for-vs-foreach/

This one adds random floating point numbers to see if the loop overhead is significant at all in the face of standard work. And, a worst-case for loop with an un-cached length counter.

Preparation HTML

<script src="http://code.jquery.com/jquery-2.1.1.min.js">
</script>

Setup

var i,
      value,
      length,
      values = [],
      sum = 0,
      context = values;
    
    
    for (i = 0; i < 10000; i++) {
      values[i] = Math.random();
    }
    
    function add(val) {
      sum += val;
    }
    
    function addEach(k, val) {
      sum += val;
    }
    
    var toString = Object.prototype.toString;
    
    function isArray(obj) {
      return toString.call(obj) === '[object Array]';
    }
    
    function isObject(obj) {
      return toString.call(obj) === '[object Object]';
    }
    
    function isString(obj) {
      return toString.call(obj) === '[object String]';
    }
    
    function each(obj, iterator) {
      var key, length;
      if (!obj) {
        return;
      }
      length = obj.length;
    
      if (isArray(obj) || isString(obj)) {
        for (key = 0; key < length; key += 1) {
          iterator(obj[key], key, obj);
        }
        return obj;
      }
    
      if (isObject(obj)) {
        for (key in obj) {
          if (obj.hasOwnProperty(key)) {
            iterator(obj[key], key, obj);
          }
        }
        return obj;
      }
    
      return obj;
    };

Teardown


    i = 0;
    value = 0;
    length = 0;
    values = [];
    sum = 0;

Test runner

Ready to run.

Testing in
TestOps/sec
forEach
values.forEach(add);
ready
for loop, cached length, callback
var arr = values,
  length = arr.length;
for (var i = 0; i < length; i++) {
  add(arr[i], i, arr);
}
ready
for loop, cached length, callback.call
length = values.length;
for (i = 0; i < length; i++) {
  add.call(context, values[i], i, values);
}
ready
$.each
$.each(values, addEach);
ready
for loop, assignment condition, callback
for (i = 0;
  (value = values[i]) !== undefined; i++) {
  add(value, i, values);
}
ready
for loop, assignment condition, callback.call
for (i = 0;
  (value = values[i]) !== undefined; i++) {
  add.call(context, value, i, values);
}
ready
native map function
values.map(add);
ready
new each
each(values, add);
ready
for loop, un-cached length, callback
var arr = values;
for (var i = 0; i < arr.length; i++) {
  add(arr[i], i, arr);
}
ready
for loop, cached length in loop,
var arr = values;
for (var i = 0, n = arr.length; i < n; i++) {
  add(arr[i], i, arr);
}
ready

Revisions

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