30-seconds-of-code/snippets/defer.md

defer

Defers invoking a function until the current call stack has cleared.

Use window.setTimeout() with a timeout of 1ms to add a new event to the browser event queue and allow the rendering engine to complete its work. Use the spread/rest (...) operator to supply the function with an arbitrary number of arguments.

const defer = (fn, ...args) => setTimeout(fn, 1, ...args);

// Example A:
defer(console.log, 'a'), console.log('b'); // logs 'b' then 'a'

// Example B:
document.querySelector('#someElement').innerHTML = 'Hello';
longRunningFunction(); // The browser will not update the HTML until this has finished
defer(longRunningFunction); // The browser will update the HTML then run the function