javascript-text-contrast

function text_contrast(hexcolor) {
  //parse hex
	var rgb = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(color);
	// Convert to RGB value between 0 and 1, and retrieve luminance
	// Alternative methods: (0.2126*R) + (0.7152*G) + (0.0722*B) or (0.299*R + 0.587*G + 0.114*B)
	var L = (0.3 * parseInt(rgb[1], 16)/255) + (0.59 * parseInt(rgb[2], 16)/255) + (0.11 * parseInt(rgb[3], 16)/255);
	console.log(L);
	return L > 0.5 ? "#000": "#FFF";
}