for vs forEach (v244)

Revision 244 of this benchmark created by Jose 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 src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.7.0/underscore-min.js">
</script>

Setup

var i,
      value,
      length,
      values = [],
      sum = 0,
      context = values;
    
    for (i = 0; i < 10000; ++i) {
      values[i] = Math.random();
    }
    
    function add(val) {
      sum += val;
    }
    
    // custom forEach
    Array.prototype.forEach2 = function(fn, c) {
    
      //if (this === void 0 || this === null || typeof fn !== 'function') throw new TypeError;
    
      var t = Object(this),
        len = t.length >>> 0,
        nc = (c === void 0 || c === null);
    
      for (var i = 0; i < len; ++i) {
        if (i in t) {
          if (nc) {
            fn(t[i], i, t)
          } else {
            fn.call(c, t[i], i, t)
          }
        }
      }
    };

Teardown


    i = 0;
    value = 0;
    length = 0;
    values = [];
    sum = 0;

Test runner

Ready to run.

Testing in
TestOps/sec
for
for (i = 0; i < values.length; ++i) {
  sum += values[i];
}
ready
for, cached length
length = values.length;
for (i = 0; i < length; ++i) {
  sum += values[i];
}
ready
for, decrement
for (i = values.length - 1; i >= 0; --i) {
  sum += values[i];
}
ready
for, decrement condition
for (i = values.length; --i;) {
  sum += values[i];
}
ready
for, post increment
for (i = 0; i < values.length; i++) {
  sum += values[i];
}
ready
for, assignment condition
for (i = 0;
  (value = values[i]) != null; ++i) {
  sum += value;
}
ready
for, = ... +
for (i = 0; i < values.length; ++i) {
  sum = sum + values[i];
}
ready
for, callback
for (i = 0; i < values.length; ++i) {
  add(values[i], i, values);
}
ready
for, callback.call
for (i = 0; i < values.length; ++i) {
  add.call(context, values[i], i, values);
}
ready
forEach
values.forEach(function(val) {
  sum += val;
});
ready
$.each
$.each(values, function(key, value) {
  sum += value;
});
ready
for ... in
for (i in values) {
  sum += values[i];
}
ready
custom forEach
values.forEach2(function(val) {
  sum += val;
});
ready
for, temoin
for (i = 0; i < values.length; ++i) {
  sum += values[i];
}
ready
underscore
_.each(values, function(val) {
  sum += val;
})
ready

Revisions

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