for vs forEach (v159)

Revision 159 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.

Preparation HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script>
Array.prototype.forEach2 = function (a, scope) {
            var l = this.length, i = 0;
            if(scope){
                for (; i < l; i++) {
                    a.call(scope, this[i], i);
                }
            }else{
                for (; i < l; i++) {
                    a(this[i], i);
                }
            }
        };
Array.prototype.forEach3 = function (a, scope) {
            var l = this.length, i = 0;
for (; i < l; i++) {
                    scope?a.call(scope, this[i], i):a(this[i], i);
                }
           
        };
</script>

Setup

var i,
      key,
      random,
      array = [],
      object = {},
      sum = 0;
    
    for (i = 0; i < 10000; i++) {
      random = Math.random();
      array[i] = random;
      object[i] = random;
    }
    
    function add(val) {
      sum += val;
    }

Teardown


    i = 0;
    array = [];
    object = {};
    sum = 0;

Test runner

Ready to run.

Testing in
TestOps/sec
forEach
array.forEach(add);
ready
for loop, simple
for (i = 0; i < array.length; i++) {
  add(array[i]);
}
ready
for loop, reverse
for (i = array.length - 1; i >= 0; i--) {
  add(array[i]);
}
ready
for key in object
for (key in object) {
  add(object[key]);
}
ready
forEach with anonymous function
array.forEach(function(val) {
  sum += val;
});
ready
foreach2
array.forEach2(add);
ready
foreach3
array.forEach3(add);
ready

Revisions

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