for vs forEach

JavaScript performance comparison

Revision 110 of this test case created

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 < 100000; i++) {
    values[i] = i;
  }

  function add(val) {
    sum += val;
  }

  function myForEach(arr, cb) {
    for (var i = 0, len = arr.length; i < len; ++i) {
      cb(arr[i])
    }
  }
</script>

Test runner

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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…
myForEach local function
var localAdd = function(val) {
  sum += val;
};
myForEach(values, localAdd);
pending…
cached, in for
for (var i = 0, len = values.length; i < len; i++) {
  add(values[i]);
}
pending…
cached, in for, pre-inc
for (var i = 0, len = values.length; i < len; ++i) {
  add(values[i]);
}
pending…
myForEach
myForEach(values, add);
pending…
myForEach closure
myForEach(values, function(val) {
  sum += val;
});
pending…
tight loop w/o fct call
for (var i = 0, len = values.length; i < len; ++i) {
  sum += values[i];
}
pending…

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