caching length

JavaScript performance comparison

Revision 7 of this test case created

Preparation code

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.14/angular.min.js"></script>
<script>
Benchmark.prototype.setup = function() {
    var arr = [];
    for (var i = 0; i < 1000; i++) {
      arr[i] = Math.random();
    }
   
   
};
</script>

Preparation code output

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Testing in unknown unknown
Test Ops/sec
cached
for (var i = 0, len = arr.length; i < len; i++) {
  arr[i] *= 2;
}
pending…
not cached
for (var i = 0; i < arr.length; i++) {
  arr[i] *= 2;
}
pending…
u wot m8
var len = 2;
len *= arr.length;
len -= len / 2;
for (var i = 0; i < len; i++) {
  arr[i] *= 2;
}
pending…
while loop
var len = arr.length;
while (len--) {
  arr[len] *= 2;
}
pending…
do-while loop
var len = arr.length;
do {
  arr[len] *= 2;
} while (len--);
pending…
Prefix Increment
for (var i = 0; i < arr.length; ++i) {
  arr[i] *= 2;
}
pending…
Prefix + Cached
for (var i = 0, len = arr.length; i < len; ++i) {
  arr[i] *= 2;
}
pending…
Array map
arr.map(function(el) {
  return el * 2;
});
pending…
iterator
function iterator(length, func) {
  for(var j = 0; j < length; j++) {
    func(j);
  }
}

iterator(arr.length, function(i) {
  arr[i] *= 2;
});
pending…
forEach element
arr.forEach(function(element, index, array) {
  element *= 2;
});
pending…
forEach index
arr.forEach(function(element, index, array) {
  array[index] *= 2;
});
pending…
angularjs
angular.forEach(arr, function(value, key) {
  value*= 2;
});
pending…
iterator2
function iterator(arr, func) {
  for(var j = 0; j < arr.length; j++) {
    func(j);
  }
}

iterator(arr, function(i) {
  arr[i] *= 2;
});
pending…
iterator3
function iterator(arr, func) {
  for(var j = 0; j < arr.length; j++) {
    func(arr[j]);
  }
}

iterator(arr, function(item) {
  item *= 2;
});
pending…
Sublime's "improved" for loop
for (var i = arr.length - 1; i >= 0; i--) {
  arr[i] *= 2;
}
pending…

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