for vs forEach

JavaScript performance comparison

Revision 159 of this test case created by

Preparation code

<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>
      
<script>
Benchmark.prototype.setup = function() {
  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;
  }

};

Benchmark.prototype.teardown = function() {
  i = 0;
  array = [];
  object = {};
  sum = 0;

};
</script>

Preparation code output

<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>

Test runner

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Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
forEach
array.forEach(add);
pending…
for loop, simple
for (i = 0; i < array.length; i++) {
  add(array[i]);
}
pending…
for loop, reverse
for (i = array.length - 1; i >= 0; i--) {
  add(array[i]);
}
pending…
for key in object
for (key in object) {
  add(object[key]);
}
pending…
forEach with anonymous function
array.forEach(function(val) {
  sum += val;
});
pending…
foreach2
array.forEach2(add);
pending…
foreach3
array.forEach3(add);
pending…

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Revisions

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