for vs $.each vs. _.each

JavaScript performance comparison

Revision 11 of this test case created

Info

Testing the time it takes to loop an array using native vs for.

Preparation code

<script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script src="//documentcloud.github.com/underscore/underscore-min.js"></script>
<script>
Benchmark.prototype.setup = function() {
    var array = new Array();  
    for (var i=0; i<100000; i++) {  
        array[i] = 0;  
    }
    // Production steps of ECMA-262, Edition 5, 15.4.4.18
    // Reference: http://es5.github.com/#x15.4.4.18
    if ( !Array.prototype.forEach ) {
     
      Array.prototype.forEach = function forEach( callback, thisArg ) {
     
        var T, k;
     
        if ( this == null ) {
          throw new TypeError( "this is null or not defined" );
        }
     
        // 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 ( {}.toString.call(callback) !== "[object 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;
     
          // 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 ( Object.prototype.hasOwnProperty.call(O, k) ) {
     
            // i. Let kValue be the result of calling the Get internal method of O with argument Pk.
            kValue = O[ k ];
     
            // 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
Native JS (for)
var l = array.length;  
for (var i=0;i<l; i++) {  
    array[i] = i;  
}
pending…
$.each
$.each (array, function (i) {  
    array[i] = i;  
});
pending…
$(array).each
$(array).each(function(i) {
    array[i] = i;
});
pending…
_.each
_.each(array, function(val, key) {
   array[key] = key;
});
pending…
Array.prototype.foreach
array.forEach(function(val, key) {
   array[key]=key;
});
pending…

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