Benchmarks in JavaScript

04 Jan 2010 | By Alex Young | Tags benchmarks libraries performance

Speeding up page load times is a good way to decrease bounce rates and increase customer satisfaction. And if you’re using JavaScript in your server-side architecture, speed will become increasingly important. So you might be tempted to write your own benchmarking code when puzzling over a tricky performance issue. Fortunately there are quite a few JavaScript benchmarking libraries out there.

Unit Tests

If you’re writing unit tests you should get some benchmark information. Most libraries automatically benchmark tests — unittest.js includes a benchmark method. You could use this outside of tests for some foresnic analysis.

JavaScript Benchmark

JavaScript Benchmark is a nice little library that features:

  • ASCII-friendly output that’s great for server-side JavaScript
  • A simple API
  • Test suite support

Each benchmark will be run once by default, or you can specify a value:

suite('Iteration', 50000, function() {
  array = [1,2,3,4,5,6,7,8,9];

  benchmark('for', function() {
    for (var i = 0; i < array.length; ++i);

  benchmark('for cached', function() {
    for (var i = 0, len = array.length; i < len; ++i);

  benchmark('for in', function() {
    for (var i in array);

This library won’t work in a browser due to the use of the print() function, but all you need to do is supply your own. Something like this will do:

function print(message) {
  document.getElementById('log').innerHTML += message + "\n";

I’ve put a full example up here: benchmarks.html


BenchmarkBuddy is inspired by the RunSingleBenchmark from the V8 source. Here’s one of the author’s examples:



Benchmark.js is based on Ruby’s benchmark library. It’s still a work in progress and isn’t currently console-friendly, but when it works it will look like this:

Benchmark.benchmark(function() {
  for (i = 0; i < 10000000; i++) { }

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