A JS library for inverting colour.

invertJS.js

/*
	invertJS (A JS library for inverting colour)

	By: Diab Neiroukh
	Licensed-under: The GNU GPLv3
	Last-updated: 23/Feb/2020
*/

function invertcolour(colour) {
	colour = colour.replace('#', '');
	if (colour.length !== 6) {
		colour = Array.prototype.join.call(arguments).match(/(-?[0-9\.]+)/g);
		for (i = 0; i < colour.length; i++) {
			colour[i] = ((i === 3 ? 1 : 255) - colour[i]);
		}
		for (j = 1; j < colour.length; j++)
			colour[j] = " " + colour[j];
		colour = "rgb(" + colour + ")";

		return colour;
	}

	colour = colour.toUpperCase();
	splitnum = colour.split("");
	resultnum = "";
	simplenum = "FEDCBA9876".split("");
	complexnum = new Array();
	complexnum.A = "5";
	complexnum.B = "4";
	complexnum.C = "3";
	complexnum.D = "2";
	complexnum.E = "1";
	complexnum.F = "0";

	for (i = 0; i < 6; i++) {
		if (!isNaN(splitnum[i])) {
			resultnum += simplenum[splitnum[i]];
		} else if (complexnum[splitnum[i]]) {
			resultnum += complexnum[splitnum[i]];
		} else {
			return false;
		}
	}

	resultnum = "#" + resultnum;
	return resultnum;
}

Add RGBA support.