If you want to time a process, you can use the console.time() and console.timeEnd() utilities specified by the console Web API. Invoking console.time() with a label starts a named timer. You can then run the process you want to time. Then invoke console.timeEnd() with the same label to terminate the timer and see how long the process took.

console.time('sorting');
[11,10,9,8,7,6,5,4,3,2,1].sort();
console.timeEnd('sorting');
> sorting: 0.278ms

console.time('console logging');
console.log('logging to the console');
console.timeEnd('console logging');
> logging to the console
> console logging: 0.311ms

console.time('adding'); 1 + 1; console.timeEnd('adding');
> adding: 0.006ms

These functions are implemented in most modern browsers.

See the docs for more details.