for vs forEach

JavaScript performance comparison

Revision 125 of this test case created by Erich Musick

Info

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

Preparation code

<script>
  var i, values = [],
      sum = 0;
  for (i = 0; i < 10000; i++) {
   values[i] = i;
  }
 
  function add(val) {
   sum += val;
  }
</script>

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Testing in unknown unknown
Test Ops/sec
forEach
values.forEach(add);
pending…
for loop, simple
for (i = 0; i < values.length; i++) {
  add(values[i]);
}
pending…
for loop, cached length
var len = values.length;
for (i = 0; i < len; i++) {
  add(values[i]);
}
pending…
for loop, reverse
for (i = values.length - 1; i >= 0; i--) {
  add(values[i]);
}
pending…
forEach more local
(function() {
  var sum = 0;
  values.forEach(function(val) {
    sum += val;
  });
})();
pending…
for...in
for (var val in values) {
  add(val);
}
pending…
for...in local
(function() {
  var sum = 0;
  for (var val in values) {
    sum += val;
  }
})();
pending…

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