How to check the number of seconds(or ms) spent inside the particular loop in javascript. I have a sorting algo implemented in javascript , now I am using bubble sort , I want to use quick sort. I know in terms of time efficiency Quick sort is good. But I want to calculate the real number of sec or milli sec spent inside the innermost loop. How do I do in javascript ?
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Addition to all the answers , one more useful functionality I found in firebug is "Timing and profiling" , getfirebug.com/logging , helps to determine JavaScript performance.sat– sat2010-10-18 08:34:41 +00:00Commented Oct 18, 2010 at 8:34
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5 Answers
All other answers in this thread are old.
Use this now, it's standard https://developer.mozilla.org/en-US/docs/Web/API/Performance.now
var t0 = performance.now();
doSomething();
var t1 = performance.now();
console.log("Call to doSomething took " + (t1 - t0) + " milliseconds.")
Comments
The simplest method is to compare by Date.
var old_time = new Date();
...
var new_time = new Date();
var seconds_passed = new_time - old_time;
By the way, why don't you just use the built-in .sort() (https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/Array/sort) method?
4 Comments
sat
ok.Thanks I am not sorting numbers , I am sorting array of objects where I sort depending on one of the property of the object. so built-in sort I cannot use.
Steve Harrison
It's worth keeping in mind that the Date object is not terribly accurate. John Resig wrote an article about this: ejohn.org/blog/accuracy-of-javascript-time.
Steve Harrison
@sat: The
sort method allows you to specify a compareFunction, which allows you to do exactly what you're after (without having to go off and create your own sorting method). See: developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/… for more information.
Lukas Liesis
This answer is out of date. Check my full answer below.
Time is not really accurate on most browsers, you can expect a margin of error about of 15ms:
var start = (new Date).getTime();
/* Your code. */
var diff = (new Date).getTime() - start;
Recommended read:
answered Jan 14, 2010 at 7:15
Christian C. Salvadó
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sat
That was a very good article !! Thanks . Never thought about it.
Others have already answered how to do the time calculation, so I'll reply to your comment: "I am sorting array of objects where I sort depending on one of the property of the object. so built-in sort I cannot use."
That's not true at all, you can still use the built in sort:
var arr = [{ text: 'test', id: 2 }, { text: 'abc', id: 6 }, { text: 'xyz', id: 4 }];
arr.sort(function(x,y) { return x.text > y.text ? 1 : x.text < y.text ? -1 : 0 });
4 Comments
sat
So in the above piece of code , its comparing the text property of 2 objects ? What algo is used internally ? means will it compare each n every object or some better algo ?
kennytm
@sat: For Firefox, merge sort. This is used instead of quick sort to ensure the sort order is stable. See bugzilla.mozilla.org/show_bug.cgi?id=224128.
kennytm
@David:
arr.sort(function(x,y) { return x.text > y.text ? 1 : x.text < y.text ? -1 : 0 });.sat
@Kenny Thanks for that great info.U get to learn lot of things with simple questions.
If you're using Firebug you can do
console.time('someNameHere');
// Do things here
console.timeEnd('someNameHere');
