The HTML5 standard specifies that the second parameter of setTimeout() must be at least 4 milliseconds, and if it is below this value, it is automatically increased. Previously, older browsers had set the minimum interval to 10 milliseconds. In addition, DOM changes, especially those that involve page re-rendering, are usually not performed immediately, but every 16 milliseconds. RequestAnimationFrame () works better than setTimeout().
Note that setTimeout() simply inserts the event into the “task queue” and must wait until the current code (stack) completes before the main thread executes its specified callback function. If the current code takes a long time, it may take a long time, so there is no guarantee that the callback will be executed at setTimeout().