jQuery.each vs. for loop

JavaScript performance comparison

Revision 220 of this test case created

Info

mdn forEach added,to prevent old IE undefined function error.....

Preparation code

<script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js">
</script>
<script>
  var a = $('*').get(),
      e;

// MDN forEach for old explorer 
if ( !Array.prototype.forEach ) {
 
  Array.prototype.forEach = function forEach( callback, thisArg ) {
 
    var T, k;
 
    // 1. Let O be the result of calling ToObject passing the |this| value as the argument.
    var O = Object(this);
 
    // 2. Let lenValue be the result of calling the Get internal method of O with the argument "length".
    // 3. Let len be ToUint32(lenValue).
    var len = O.length >>> 0; // Hack to convert O.length to a UInt32
 
    // 4. If IsCallable(callback) is false, throw a TypeError exception.
    // See: http://es5.github.com/#x9.11
    if ( typeof callback != "function" ) {
      throw new TypeError( callback + " is not a function" );
    }
 
    // 5. If thisArg was supplied, let T be thisArg; else let T be undefined.
    if ( thisArg ) {
      T = thisArg;
    }
 
    // 6. Let k be 0
    k = 0;
 
    // 7. Repeat, while k < len
    while( k < len ) {
 
      var kValue, Pk;
      Pk=String(k);

      // a. Let Pk be ToString(k).
      //   This is implicit for LHS operands of the in operator
      // b. Let kPresent be the result of calling the HasProperty internal method of O with argument Pk.
      //   This step can be combined with c
      // c. If kPresent is true, then
      if ( O.hasOwnProperty(Pk) ) {
 
        // i. Let kValue be the result of calling the Get internal method of O with argument Pk.
        kValue = O[ Pk ];
 
        // ii. Call the Call internal method of callback with T as the this value and
        // argument list containing kValue, k, and O.
        callback.call( T, kValue, k, O );
      }
      // d. Increase k by 1.
      k++;
    }
    // 8. return undefined
  };
}
</script>

Preparation code output

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Testing in unknown unknown
Test Ops/sec
jQuery.each
 
$.each(a, function() {
  e = this;
});
 pending…
for loop
 
for (var i = 0, len = a.length; i < len; i++) {
  e = a[i];
};
 pending…
for without caching
 
for (var i = 0; i < a.length; i++) {
  e = a[i];
};
 pending…
alternative for loop
 
for (var i in a) {
  e = a[i];
};
 pending…
reverse for
 
for (var i = a.length; i--;) {
  e = a[i];
}
 pending…
reverse while
 
var i = a.length
while (i--) {
  e = a[i];
}
 pending…
foreach
 
a.forEach(function(elem) {
  e = elem;
});
 pending…
for sublime
 
for (var i = a.length - 1; i >= 0; i--) {
  e = a[i]
};
 pending…

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