@lagrange/animator/src/functions/getInitialMatrix.js

This library helps making parallax animations on scroll. It is built with performance in mind, as it doesn't need to relayout or paint to operate.

import { fromString, matrix2dto3d } from '../utils/CssMatrix';

/**
 * @param {HTMLElement} elem 
 */
export function getInitialMatrix(elem, is3D = false) {
	const prev = elem.style.transform;
	elem.style.transform = '';
	const transform = window.getComputedStyle(elem).getPropertyValue('transform');
	elem.style.transform = prev;
	
	if (transform === 'none') return null;

	let m = fromString(transform);
	m = (m.length < 16 && is3D) ? matrix2dto3d(m) : m;
	
	return m;
}