in vs typeof Direct Comparison

JavaScript performance comparison

Test case created by Jason Mulligan

Preparation code

<script>
  var x = {a: true},
      y = false;
</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
in (invalid)
return ("y" in x);
pending…
in (valid)
return ("a" in x);
pending…
typeof (invalid)
return (typeof x.y !== "undefined");
pending…
typeof (valid)
return (typeof x.a !== "undefined");
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