Underscore.each vs jQuery.each vs. for loop vs. forEach

JavaScript performance comparison

Revision 99 of this test case created

Info

All test assume you want to do something with the loop index, the relative item in the array, and the resulting array.

Preparation code

<script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js">
</script>
<script src="//documentcloud.github.com/underscore/underscore-min.js">
</script>
<script>
  var pi = Math.PI,
      a = new Array(1000000),
      o,
      e,
      r;

var f_each = function(a, fn) {
    for (var i = 0, l = a.length; i < l; i++) {
        fn(a[i], i);
    }
    return a;
}


</script>

Preparation code output

Test runner

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Testing in unknown unknown
Test Ops/sec
jQuery.each
 
r = $.each(a, function(i, it) {
  o = it;
  e = pi + i;
  a[i] = e;
});
 pending…
good old for loop
 
for (var item, i = 0, len = a.length; i < len; i++) {
  o = a[i]
  e = pi + i;
  a[i] = e;
};
r = a;
 pending…
underscore.each
 
_.each(a, function(it, i) {
  o = it;
  e = pi + i;
  a[i] = e;
});
r = a;
 pending…
good old for loop (decrementing)
 
var i = a.length;
for (; i > 0; i--) {
  o = a[i]
  e = pi + i;
  a[i] = e;
};
r = a;
 pending…
forEach
 
a.forEach(function(it, i) {
  it = a[i]
  e = pi + i;
  a[i] = e;
});
r = a;
 pending…
functional
 
r = f_each(a, function(it, i) {
    o = it;
    e = pi + i;
    a[i] = e;
});
 pending…

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