Info

Previous tests were also testing fn construction, not just pure array construction. This differs from http://jsperf.com/slice-vs-copy/ in that these are all function invocations, not just inline (which is basically always faster under 10 members).

Pre-allocating the target array length, see http://jsperf.com/pre-allocationg-vs-literal. Note, the length of the array matters greatly, see http://jsperf.com/slice-vs-copy/ in the revisions/notes.

Preparation code

 
<script>
  Benchmark.prototype.setup = function() {
    var arr = new Array(1, 2, 3, 4, 5);
    
    function forinclone(arr) {
      var key, arr_clone = new Array(arr.length);
      for (key in arr) {
        arr_clone[key] = arr[key];
      }
      return arr_clone;
    }
    
    function forclone(arr) {
      var i, len = arr.length,
          arr_clone = new Array(len);
      for (i = 0; i < len; i += 1) {
        arr_clone[i] = arr[i];
      }
      return arr_clone;
    }
    
    function pushforclone(arr) {
      var i, len = arr.length,
          arr_clone = [];
      for (i = 0; i < len; i += 1) {
        arr_clone.push(arr[i]);
      }
      return arr_clone;
    }
    
    function whileclone(arr) {
      var len = arr.length,
          arr_clone = new Array(len);
      while (len--) {
        arr_clone[len] = arr[len];
      }
      return arr_clone;
    }
  };
</script>

Test runner

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Java applet disabled.

arr_clone = forinclone(arr);

arr_clone = arr.slice();

arr_clone = arr.concat();

arr_clone = forclone(arr);

arr_clone = pushforclone(arr);

arr_clone = whileclone(arr);

arr_clone = [];
arr_clone.push.apply(arr_clone, arr);

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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 2: published by keville on 24th February 2012
• Revision 3: published on 1st March 2012
• Revision 4: published by Paul Grenier on 1st March 2012
• Revision 5: published on 3rd March 2012
• Revision 6: published on 27th December 2012
• Revision 7: published by Jonathan Perry on 27th December 2012
• Revision 9: published on 11th March 2013

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