Array unshift vs prepend

JavaScript performance comparison

Test case created

Preparation code

<script>
  var a;
  var prependArray = function(value, oldArray) {
   var i, len = oldArray.length + 1,
       newArray = new Array(len);
   newArray[0] = value;
   for (i = 0; i < len; ++i) {
    newArray.push(oldArray[i]);
   }
   return newArray;
  }
</script>

Test runner

Warning! For accurate results, please disable Firebug before running the tests. (Why?)

Java applet disabled.

Testing in unknown unknown
Test Ops/sec
Unshift
 
a = [1, 2, 3, 4];
a.unshift(0);
 pending…
Prepend function
 
a = [1, 2, 3, 4];
prependArray(0, a);
 pending…
Unshift without mutation
 
a = [1, 2, 3, 4];
a.slice(0).unshift(0);
 pending…

Compare results of other browsers

Revisions

You can edit these tests or add even more tests to this page by appending /edit to the URL. Here’s a list of current revisions for this page:

0 comments

Add a comment