javascript convert any color to array of rgba values

colorValues.js

// return array of [r,g,b,a] from any valid color. if failed returns undefined
function colorValues(color)
{
	if (!color)
		return;
	if (color.toLowerCase() === 'transparent')
		return [0, 0, 0, 0];
	if (color[0] === '#')
	{
		if (color.length < 7)
		{
			// convert #RGB and #RGBA to #RRGGBB and #RRGGBBAA
			color = '#' + color[1] + color[1] + color[2] + color[2] + color[3] + color[3] + (color.length > 4 ? color[4] + color[4] : '');
		}
		return [parseInt(color.substr(1, 2), 16),
			parseInt(color.substr(3, 2), 16),
			parseInt(color.substr(5, 2), 16),
			color.length > 7 ? parseInt(color.substr(7, 2), 16)/255 : 1];
	}
	if (color.indexOf('rgb') === -1)
	{
		// convert named colors
		var temp_elem = document.body.appendChild(document.createElement('fictum')); // intentionally use unknown tag to lower chances of css rule override with !important
		var flag = 'rgb(1, 2, 3)'; // this flag tested on chrome 59, ff 53, ie9, ie10, ie11, edge 14
		temp_elem.style.color = flag;
		if (temp_elem.style.color !== flag)
			return; // color set failed - some monstrous css rule is probably taking over the color of our object
		temp_elem.style.color = color;
		if (temp_elem.style.color === flag || temp_elem.style.color === '')
			return; // color parse failed
		color = getComputedStyle(temp_elem).color;
		document.body.removeChild(temp_elem);
	}
	if (color.indexOf('rgb') === 0)
	{
		if (color.indexOf('rgba') === -1)
			color += ',1'; // convert 'rgb(R,G,B)' to 'rgb(R,G,B)A' which looks awful but will pass the regxep below
		return color.match(/[\.\d]+/g).map(function (a)
		{
			return +a
		});
	}
}

/* 
Examples:

    colorValues('transparent'); // [0,0,0,0]
    colorValues('white'); // [255, 255, 255, 1]
    colorValues('teal'); // [0, 128, 128, 1]
    colorValues('rgba(11,22,33,.44)'); // [11, 22, 33, 0.44]
    colorValues('rgb(11,22,33)'); // [11, 22, 33, 1]
    colorValues('#abc'); // [170, 187, 204, 1]
    colorValues('#abc6'); // [170, 187, 204, 0.4]
    colorValues('#aabbcc'); // [170, 187, 204, 1]
    colorValues('#aabbcc66'); // [170, 187, 204, 0.4]
    colorValues('asdf'); // undefined
    colorValues(''); // undefined
    colorValues(NaN); // Script Error
    colorValues(123); // Script Error
*/

Link to StackOverflow:
https://stackoverflow.com/a/44655529/3356679

great thanks for this)

Very good and consise! Thanks

Nice one. I made a much shorter version that even accepts hsl and hexa colors:
https://gist.github.com/av01d/8f068dd43447b475dec4aad0a6107288