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

JavaScript performance comparison

Revision 74 of this test case created

Info

Fast alternative to $.fn.each(func). Most usage of fn.each immediately evaluates $(this) - which is really expensive. This version changes this so that it already points to a single-element jQuery object.

Notes:

My previous implementation (48) was bobbins because modern JS engines use short-circuiting to avoid doing work ... and there was a bug that you could drive a bus through.

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>')).children();
  var arr = $.makeArray(a);

  jQuery.fn.betterEach = (function() {
    var jq = jQuery([1]);
    var slice = Array.prototype.slice;
    var el;
    return function(c) {
       var iter = function(e, i) {
         el = jq[0] = e;
         c.call(jq, i, el);
       };
       slice.call(this).forEach(iter);
       jq[0] = 1;
       return this;
    }
  })();

  // Modified quickEach plugin
  jQuery.fn.quickerEach = (function() {
    var jq = jQuery([1]);
    return function(c) {
      var i = -1, el;
      try {
        while (el = jq[0] = this[++i] && c.call(jq, i, el) !== false);
      } catch (e) {
        jq[0] = 1;
        throw e;
      }
      jq[0] = 1;
      return this;
    };
  }());
  // Modified quickEach plugin
  jQuery.fn.quickerEach2 = (function() {
    var jq = jQuery([1]);
    return function(c) {
      var i = -1, el;
      try {
        while (el = jq[0] = this[++i]&& c.call(jq[0], i, el) !== false);
      } catch (e) {
          jq[0] = 1;
        throw e;
      }      
        jq[0] = 1;
      return this;
    };
  }());

  jQuery.fn.quickerEach3 = (function() {

    return function(c) {
      var i = -1, el;
      try {
        while (el = this[++i] && c.call(el, i) !== false);
      } catch (e) {
        throw e;
      }
      return this;
    };
  }());

  // James Padolsey's quickEach plugin
  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;
    };
  }());


</script>

Preparation code output

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Testing in unknown unknown
Test Ops/sec
.each()
 
var count = 0;
a.each(function() {
  this.className += ' fred';
});
 pending…
.quickEach()
 
a.quickEach(function() {
  this[0].className += ' fred';
});
 pending…
.quickerEach()
 
a.quickerEach(function() {
  this[0].className += ' fred';
});
 pending…
For loop
 
//Note that this may be more suitable for your needs.
var jq = jQuery([1]);
for (var i = 0, len = a.length; i < len; i++) {
  a[i].className += ' fred';
}
//For fastest performance - avoid jQuery and go direct to the DOM.
 
 pending…
quickerEach2
 
a.quickerEach2(function() {
  this.className += ' fred';
});
 pending…
quickerEach3
 
a.quickerEach3(function() {
  this.className += ' fred';
});
 pending…

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Revisions

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1 comment

Andy Harman commented : ∞

Several of the tests have errors: while (el = jq[0] = this[++i]&& c.call(jq[0], i, el) !== false); Should be: while ((el = jq[0] = this[++i]) && c.call(jq[0], i, el) !== false);

I think that the author may have based this revision on my buggy revision.

Also, the whole point of this test scenario is to create a version of $().each() that provides a jQuery object to the called-method, rather than a DOM element.

Revision 69 is still the best example.

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