Javascript hex to rgb()/rgba()

rgba()

// Please note this uses my Math.range and String.regex methods
	/**
	 * Convert a hex colour to a rgb/rgba value
	 * @param {string} hex
	 * @param {?number} opacity
	 * @returns {string}
	 */
	function rgba(hex, opacity) {
		var colours = hex.regex(/#?([0-9A-F]{2})([0-9A-F]{2})([0-9A-F]{2})/i).map(function(val) {
			return Math.range(0, parseInt(val, 16), 255);
		}).join(",");
		if (opacity === undefined) {
			return "rgb(" + colours + ")";
		}
		return "rgba(" + colours + "," + opacity + ")";
	}

Where does the range method come from? I can't find it in the documents for Math