JavaScript - measure elapsed time between setInterval() intervals

In this article, we would like to show you how to measure elapsed time between setInterval() intervals using JavaScript.

Quick solution:

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let startTime = Date.now();

setInterval(() => {

    let endTime = Date.now();

    let timeSpan = endTime - startTime;

    console.log(timeSpan);

    startTime = endTime;

}, 1000);

Warning:

This API does not guarantee that timers will run exactly on schedule. Delays due to CPU load, other tasks, etc, are to be expected.

In this example, as an alternative solution, we use performance.now() to measure the time elapsed between intervals.

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var startTime = performance.now();

setInterval(() => {

    var endTime = performance.now();

    var timeSpan = endTime - startTime;

    console.log(timeSpan);

    startTime = endTime;

}, 1000);

References

1. setInterval() - Web APIs | MDN
2. performance.now() - Web APIs | MDN
3. HTML Standard