How can I check/compare my JavaScript code speed/performance?

Question

Is there any way to check/compare JavaScript codes' performances on my pc/browser?

Like,

Method 1:

var x = 3;
if (x === 1) {
  console.log(1);
} else {
  console.log(2);
}

Method 2:

var x = 3;
switch (a) {
  case 1: 
    console.log(1);
    break; 
  default: 
    console.log(2);
  }

Here, 'Method 1' and 'Method 2' both does the same thing, and if I search on the internet there might be several benchmarks to prove which method is faster/efficient.

But I want to check it myself (offline methods, i mean on my pc would be better for me).

Thanks :)

Thanks, I've seen that, but is there any way I can do that on my browser/pc? Like Chrome Dev Tools has a lots of features, Does it supports those performance checking too? — MARUF
– MARUF, Commented Aug 9, 2015 at 8:53
@MARUF: Chrome's dev tools have performance stuff in them, yes, but as a one-off you're not going to see enough difference to measure. You'd have to use a loop, which opens you up to all kinds of problems because what you're testing is synthetic rather than real. — T.J. Crowder
– T.J. Crowder, Commented Aug 9, 2015 at 9:02
@MARUF: FYI, unlike C or Java, switch and if/else if/else are effectively the same thing in JavaScript. I'd expect your two code examples above, if they were identified as performance-critical, to end up being compiled to the same machine code by Chrome's V8 engine, for instance. — T.J. Crowder
– T.J. Crowder, Commented Aug 9, 2015 at 9:04
@MARUF: Instead of micro-optimizing ahead of time, respond to performance issues in the real code if and when they occur. — T.J. Crowder
– T.J. Crowder, Commented Aug 9, 2015 at 9:04

Gaushick · Accepted Answer · 2016-06-09 07:12:05Z

1

Yes, you can check the performance by using "console.time"

Try this,

For Method 1 :

console.time('Method #1');

var x = 3;
if (x === 1) {
  console.log(1);
} else {
  console.log(2);
}

console.timeEnd('Method #1');

For Method 2:

console.time('Method #2');

var x = 3;
switch (a) {
 case 1: 
   console.log(1);
 break; 
default: 
   console.log(2);
}

console.timeEnd('Method #2');

answered Jun 9, 2016 at 7:12

Gaushick

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4 Comments

robertklep Over a year ago

I doubt that that will yield any reasonable timings. Better run each method a few 100K times

zerkms Over a year ago

@robertklep it definitely will not, since modern engines (de)optimise as code warms up.

robertklep Over a year ago

@zerkms yeah, even those "100K" iterations will probably not yield any really useful results with this code.

zerkms Over a year ago

@robertklep there is a good chance both will be optimised to something very similar if not identical :-)

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