How to time functions in JavaScript similar to Python timeit

Question

How can I measure the execution time of functions in JavaScript? Preferably similar to Python timeit.

Answer 1

There is no built in module equivalent to timeit.py but you can easily time the execution of code yourself. You should use performance.now() rather than Date.now() as it is more accurate.

From the MDN docs:

The performance.now() method returns a DOMHighResTimeStamp, measured in milliseconds, accurate to five thousandths of a millisecond (5 microseconds)

var start = performance.now();

//do your things

var end = performance.now();
var duration = end - start;

You could then use that to build your own timing library like this:

function TimeIt() {
    var self = this;

    function howLong(iterations, testFunction) {
        var results = [];
        var total = 0;
        for (var i = 0; i < iterations; i++) {
            var start = performance.now();
            testFunction();
            var end = performance.now();
            var duration = end - start;
            results.push(duration);
            total += duration;
        }
        var result = {
                results : results,
                total : total,
                avg : total / results.length
        }
        return result;
    }
    self.howLong = howLong;
}

Which you would use like this:

var timeit = new TimeIt();

var foo = function() {
//do some things
};

var result = timeit.howLong(1000, foo);
console.log("avg: " + result.avg);
console.log("total: " + result.total);

Answer 2

I haven't made a really deap search about it, but as far as I have searched, I haven't found anything. The simplest thing to do is, get time when the function starts, get time when it ends and substract one from the other(after using Date.parse to convert them in miliseconds) . It is certainly a naive solution but a working one.