caching length

JavaScript performance comparison

Revision 107 of this test case created by

Preparation code


      
      <script>
Benchmark.prototype.setup = function() {
  "use strict";
  var arr = [];
  for (var i = 0; i < 20; i++) {
    arr[i] = Math.random();
  }

};
</script>

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Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
not cached (basic)
"use strict";
for (let i = 0; i < arr.length; i++) {
  arr[i] *= 2;
}
pending…
cached length
"use strict";
for (let i = 0, len = arr.length; i < len; i++) {
  arr[i] *= 2;
}
pending…
prefix increment
"use strict";
for (let i = 0; i < arr.length; ++i) {
  arr[i] *= 2;
}
pending…
prefix increment + cached length
"use strict";
for (let i = 0, len = arr.length; i < len; ++i) {
  arr[i] *= 2;
}
pending…
decrement
"use strict";
for (let i = arr.length - 1; i > -1; i--) {
  arr[i] *= 2;
}
pending…
decrement without final-expression
"use strict";
for (let i = arr.length; i--!==0;) {
   arr[i] *= 2;
}
pending…
.forEach()
"use strict";
arr.forEach(function(element, i, array) {
 array[i] *= 2;
});
pending…
for in
"use strict";
for(var i in arr) {
  arr[i] *= 2;
}
pending…
.shift() (building new array)
"use strict";
var ar = [];

while (let dee = arr.shift()) {
  ar.push(dee * 2);
}
pending…
while loop
"use strict";
let len = arr.length;
while (len--) {
  arr[len] *= 2;
}
pending…
cached length + not equal
"use strict";
for (let i = 0, len = arr.length; i !== len; i++) {
  arr[i] *= 2;
}
pending…

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