How to measure time elapsed on Javascript? [duplicate]

Question

I created a simple game that start and ends the timer when the user finishes clicking on 16 boxes.

I want to measure the elapsed time for the user to complete the game. How do I do it using Javascript?

I took a look at different answers like this, but I had hard time understanding others' code.

I would assume it to look like this.

Timer Start: When user clicks the first box Timer End: When user clicks the last box 

Answer 1

The Date documentation states that :

The JavaScript date is based on a time value that is milliseconds since midnight January 1, 1970, UTC

Click on start button then on end button. It will show you the number of seconds between the 2 clicks.

The milliseconds diff is in variable timeDiff. Play with it to find seconds/minutes/hours/ or what you need

var startTime, endTime;    function start() {    startTime = new Date();  };    function end() {    endTime = new Date();    var timeDiff = endTime - startTime; //in ms    // strip the ms    timeDiff /= 1000;      // get seconds     var seconds = Math.round(timeDiff);    console.log(seconds + " seconds");  }

<button onclick="start()">Start</button>    <button onclick="end()">End</button>

OR another way of doing it for modern browser

Using performance.now() which returns a value representing the time elapsed since the time origin. This value is a double with microseconds in the fractional.

The time origin is a standard time which is considered to be the beginning of the current document's lifetime.

var startTime, endTime;    function start() {    startTime = performance.now();  };    function end() {    endTime = performance.now();    var timeDiff = endTime - startTime; //in ms     // strip the ms     timeDiff /= 1000;         // get seconds     var seconds = Math.round(timeDiff);    console.log(seconds + " seconds");  }

<button onclick="start()">Start</button>  <button onclick="end()">End</button>