Info

Comparison of different ways to treat the length of an array when iterating the array.

Preparation code

<script src="//cdnjs.cloudflare.com/ajax/libs/lodash.js/1.0.0-rc.3/lodash.min.js"></script>
<script>
  Benchmark.prototype.setup = function() {
    window.list = [];
    var x = 100;
    for (var y = 0; y < x; y++) {
      window.list[y] = true;
    }
  };

  Benchmark.prototype.teardown = function() {
    delete window.list;
  };
</script>

Test runner

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for (var i = 0; i < window.list.length; i++) {
  var fruit = window.list[i];
}

var len = window.list.length;
for (var i = 0; i < len; i++) {
  var fruit = window.list[i];
}

for (var i = 0, len = window.list.length; i < len; i++) {
  var fruit = window.list[i];
}

for (var i = window.list.length; i--;) {
  var fruit = window.list[i];
}

var i = window.list.length;
while (i--) {
  var fruit = window.list[i];
}

var i = window.list.length;
for (; i--;) {
  var fruit = window.list[i];
}

var i = window.list.length,
    fruit;
for (; i >= 0; i--) {
  fruit = window.list[i];
}

var list = window.list.slice(0),
    fruit = list.shift();
while (fruit) {
  fruit = list.shift();
}

var list = window.list.slice(0),
    fruit = list.pop();
while (fruit) {
  fruit = list.pop();
}

var list = window.list.slice(0).reverse(),
    fruit = list.pop();
while (fruit) {
  fruit = list.pop();
}

_.times(window.list.length, function (i) {

  var fruit = window.list[i];
});

_.each(window.list, function (item) {

  var fruit = item;
});

Compare results of other browsers

Revisions

You can edit these tests or add even more tests to this page by appending /edit to the URL. Here’s a list of current revisions for this page:

• Revision 1: published on 7th August 2011
• Revision 2: published on 7th August 2011
• Revision 3: published on 9th May 2012
• Revision 4: published on 26th July 2012
• Revision 5: published on 26th July 2012
• Revision 6: published by Vance Ingalls on 27th September 2012
• Revision 7: published on 27th September 2012
• Revision 8: published by Vance Ingalls on 27th September 2012
• Revision 9: published by Raymond on 30th January 2013
• Revision 10: published on 6th February 2013
• Revision 11: published 2 weeks ago
• Revision 12: published 2 weeks ago

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