Firebug’s console.time()
As I wrote in my previous post Firebug is giving the ability to test performance of any chunk of JavaScript code with its console.time() method. One of the most discussed topics about performance and one of the most recently examples given in the web is the way to instanciate a new empty array in JavaScript.
new Array() vs. []
Which one is faster? This is the question we’ve seen so many times in the web. I decided to check it with the console.time() method. For my experiment I made 100000 new arrays both way:
var arr = new Array();
and
var arr = [];
Thus the sample code of the first experiment is:
<html>
<body>
<script>
console.time('profile 1');
for ( var i=0; i < 100000; i++) {
var arr = new Array();
}
console.timeEnd('profile 1');
</script>
</body>
</html>
and the results are 12 ms. OK, so far so good. Now I’d like to test the same construction with the other way to make new array instance:
<html>
<body>
<script>
console.time('profile 2');
for ( var i=0; i < 100000; i++) {
var arr = [];}
console.timeEnd('profile 2');
</script>
</body>
</html>
And the result is pretty much the same – 11 ms. That’s why I choose to increase the number of iterations of this loop from 100,000 to 10,000,000 and the second chunk of code using the construction arr = [] is finishing its job for around 3400ms or a little bit more than 3 seconds, while the first one is a little bit faster – 2450ms or faster with almost a second.
What if we merge both chunks?
I decided to concatenate the code in something like:
<html>
<body>
<script>
console.time('profile 1');
for ( var i=0; i < 100000; i++) {
var arr = new Array();
}
console.timeEnd('profile 1');
console.time('profile 2');
for ( var i=0; i < 100000; i++) {
var arr = [];
}
console.timeEnd('profile 2');
</script>
</body>
</html>
results:
and yet again the same results as if they were separated tests, which of course seems to be pretty natural.
Use console.time()!
That’s the way to get clear example of how fast your code is. Actually this is not a pure sense profile, where you can get minimum and maximum performance times but it gives pretty accurate values.
Hi. Thank you for this text … i looking for something just like this 🙂
thank you so much!! was looking for this commands 🙂