javascript - performance.now() vs Date.now()

Question

What is the difference between performance.now() and Date.now()?

Should I consider performance.now() as a replacement for Date.now() since performace.now() is more consistent and independent?

Answer 1

They both serve different purposes.

performance.now() is relative to page load and more precise in orders of magnitude. Use cases include benchmarking and other cases where a high-resolution time is required such as media (gaming, audio, video, etc.)

It should be noted that performance.now() is only available in newer browsers (including IE10+).

Date.now() is relative to the Unix epoch (1970-01-01T00:00:00Z) and dependent on system clock. Use cases include same old date manipulation ever since the beginning of JavaScript.

See When milliseconds are not enough: performance.now and now method (Internet Explorer) - MSDN for more information.

The official W3C spec can be found here: High Resolution Time API