Igor Kamyşev igorkamyshev

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

	// https://reactjs.org/docs/hooks-faq.html#how-to-read-an-often-changing-value-from-usecallback
	// https://github.com/reactjs/rfcs/pull/220#issuecomment-1259938816

	import React from 'react';

	// Allow to access a fresh closures in the function but returns stable reference during rerenders
	export function useCallbackRef<T extends (...args: unknown[]) => unknown>(callback: T): T {
	const ref: React.MutableRefObject<{
	stableFn: T;
	callback: T;