How can I measure the execution time of a script?

Question

How would I measure the time it takes for a script to run from start to finish?

 start-timing
   //CODE
 end-timing

Remember, a grammatically correct title and relevant tags makes all the difference. — ChaosPandion, Jan 24 '11 at 17:06
Does this answer your question? [How to measure time taken by a function to execute](https://stackoverflow.com/questions/313893/how-to-measure-time-taken-by-a-function-to-execute) — Donald Duck, Jul 22 '20 at 08:32

score 52 · Accepted Answer · edited May 11 '16 at 06:44

52

EDIT: in January 2011, this was the best available solution. Other solutions (such as performance.now() should be preferred now.

var start = new Date();
    // CODE
var time = new Date() - start;
// time is the number of milliseconds it taken to execute the script

You may also want to wrap that in a function:

function time_my_script(script) {
    var start = new Date();
    script();
    return new Date() - start;
}

// call it like this:
time = time_my_script(function() {
    // CODE
});

// or just like this:
time = time_my_script(func);

If you are trying to profile your code, you may want to try the Firebug extension, which includes a javascript profiler. It has a great user interface for profiling, but it also can be done programmatically with its console api :

console.time('timer1');
    // CODE
console.timeEnd('timer1'); // this prints times on the console

console.profile('profile1');
    // CODE
console.profileEnd('profile1'); // this prints usual profiling informations, per function, etc.

edited May 11 '16 at 06:44

Pierre Arnaud

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answered Jan 24 '11 at 17:02

Arnaud Le Blanc

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You don't need to call `getTime()`: using the `-` operator converts each `Date` object to its time value anyway. For example, `return new Date() - start;` – Tim Down Jan 24 '11 at 17:35
Amazes me how sometimes the solutions are sooooo simple and elegant! :-) – ankush981 Jul 05 '15 at 08:40
1

`performance.now()` should be preferred over `new Date()` - see other answer by Morteza Ziaeemehr. – Pierre Arnaud May 10 '16 at 12:23
@PierreArnaud please check the date before down voting (: – Arnaud Le Blanc May 10 '16 at 13:02
@arnaud576875 you are right - I added a note at the beginning of your answer to clearly indicate that the answer dates back to 01.2011. And that other solutions exist today. – Pierre Arnaud May 11 '16 at 06:45

score 11 · Answer 2 · edited May 23 '17 at 12:00

11

Use performance.now() instead of new Date(). This provides a more accurate and better result. See this answer https://stackoverflow.com/a/15641427/730000

edited May 23 '17 at 12:00

Community

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answered Nov 24 '14 at 16:36

Morteza

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score 2 · Answer 3 · answered Apr 24 '18 at 20:57

Use the User Timing api

For example: in the beginning of the JS file write: performance.mark("start-script")

at the end of the JS file write: performance.mark("end-script")

then you can measure it too:

performance.measure("total-script-execution-time", "start-script", "end-script");

This will give you the time it takes to run the entire script execution.

score 0 · Answer 4 · answered Feb 25 '17 at 14:20

Here is a quick function to work like a stopwatch

var Timer = function(id){
  var self = this;
  self.id  = id;
  var _times = [];
  self.start = function(){
    var time = performance.now();
    console.log('[' + id + '] Start');
    _times.push(time);
  }
  self.lap = function(time){
    time = time ? time: performance.now();
    console.log('[' + id + '] Lap ' + time - _times[_times.length - 1]);
    _times.push(time);
  }
  self.stop = function(){
    var time = performance.now();
    if(_times.length > 1){
      self.lap(time);
    }
    console.log('[' + id + '] Stop ' + (time - _times[0]));
    _times = [];
  }
}
// called with
var timer = new Timer('process label');
timer.start(); // logs => '[process label] Start'
// ... code ...
timer.lap();   // logs => '[process label] Lap ' + lap_time
// ... code ...
timer.stop();  // logs => '[process label] Stop ' + start_stop_diff

How can I measure the execution time of a script?

4 Answers4

Use the User Timing api

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