jQuery.fn.each vs. jQuery.fn.quickEach

JavaScript performance comparison

Revision 70 of this test case created

Info

The quickEach method will pass a non-unique jQuery instance to the callback meaning that there will be no need to instantiate a fresh jQuery instance on each iteration. Most of the slow-down inherent in jQuery’s native iterator method (each) is the constant need to have access to jQuery’s methods, and so most developers see constructing multiple instances as no issue… A better approach would be quickEach.

My previous test case was bobbins - so we're back to James Padolsey's original quickEach - and the fact that in many scenarios it is about the same speed as a simple while loop.

Have added "Cowboy" Ben Alman's version for comparison.

Preparation code

<script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js">
</script>
<script>
  var a = $('<div/>').append(Array(100).join('<a></a>')).find('a');

  //Original version by James Padolsey.
  //The try/catch and delete were designed to ensure no memory leak.
  jQuery.fn.quickEach = (function() {
    var jq = jQuery([1]);
    return function(c) {
      var i = -1,
          el, len = this.length;
      try {
        while (++i < len && (el = jq[0] = this[i]) && c.call(jq, i, el) !== false);
      } catch (e) {
        delete jq[0];
        throw e;
      }
      delete jq[0];
      return this;
    };
  }());

/*!
   * jQuery each2 - v0.2 - 8/02/2010
   * http://benalman.com/projects/jquery-misc-plugins/
   *
   * Inspired by James Padolsey's quickEach
   * http://gist.github.com/500145
   *
   * Copyright (c) 2010 "Cowboy" Ben Alman
   * Dual licensed under the MIT and GPL licenses.
   * http://benalman.com/about/license/
   */

  (function($) {
    // Create a placeholder jQuery object with a length of 1. The single item
    // is completely arbitrary and will be replaced.
    var jq = $([1]);

    $.fn.each2 = function(fn) {
      var i = -1;

      while (
      // Set both the first element AND context property of the placeholder
      // jQuery object to the DOM element. When i has been incremented past the
      // end, this[++i] will return undefined and abort the while loop.
      (jq.context = jq[0] = this[++i])

      // Invoke the callback function in the context of the DOM element,
      // passing both the index and the placeholder jQuery object in. Like
      // .each, if the callback returns `false`, abort the while loop.
      && fn.call(jq[0], i, jq) !== false) {}

      // Return the initial jQuery object for chainability.
      return this;
    };
  })(jQuery);


  /*
   * (cc:by) Artūrs Jansons
   */

  jQuery.fn.each3 = (function() {
    return function(c) {
      for(x in this){
        !(++x) || c.call(this,x,this[x]) !== false
      }
      return this
    }
  }());
</script>

Preparation code output

Test runner

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Testing in unknown unknown
Test Ops/sec
.each
a.each(function() {
  $(this).addClass("wibble");
});
pending…
Original .quickEach
//Implementation by James Padolsey.
a.quickEach(function() {
  this.addClass("wibble"); // jQuery object
});
pending…
original each2
//Implemented by "Cowboy" Ben Alman.
a.each2(function(i, jq) {
  jq.addClass("wibble"); // jQuery object
});
pending…
for loop 1
//$([DomElement]) is faster than $([1]) - we are going to discard
//jq variable after loop has finished so possibility of zero-length
//is not important.
var jq = jQuery(a[0]);
for (var i = 0; i < a.length; i++) {
  jq[0] = a[i];
  jq.addClass("wibble");
}
pending…
for loop 2
//What's the cost of instantiating jQuery object?
//About 25% when you have addClass() inside the loop.
for (var i = 0; i < a.length; i++) {
  var jq = $(a[i]);
  jq.addClass("wibble");
}
pending…
while loop
var jq = jQuery(a[0]),
    i = -1;
while (jq[0] = a[++i]) {
  jq.addClass("wibble");
}
pending…
for-in loop
var jq = jQuery(a[0])
for (x in jq) {
  jq.addClass("wibble");
}
pending…
.each3
a.each3(function(){
  $(this).addClass("wibble");
})
pending…

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Revisions

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