If you’ve heard about console.time before, you can just close the tab. :)

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JavaScript console.time is a great built-in tool that gives you the duration of an operation.

Usage

console.time starts the timer, and console.timeEnd stops it, so just wrap what you want to measure between these methods, and you should see the result in the console.

The output is in suitable time units. For example, if the elapsed time is 3869ms, console.timeEnd displays "3.869s".

And here’s a real example: as you can see, foo took 1ms to finish looping through an array of 10,000 empty values.