Convert CSS values to a usable number, parses calc() for a single depth only

convertCSS

/**
 * Convert a css number type string into pixel units
 * @param {jQuerySelector} $el
 * @param {String} value
 * @param {?Boolean} horiz
 * @returns {Number}
 */
function convertCSS($el, value, horiz) {
	var val = parseFloat(value);
//	console.log("convertCSS", value, value.replace(/[^a-z%]/g, ""), horiz)
	switch (value.replace(/[^a-z%]/g, "").substr(0, 4)) {
		case "none":
			val = 0;
			break;
		case "calc":
			var operand, num,
					sum = value.replace(/^calc\(|\)$/g, "").split(" ");
			val = convertCSS($el, sum.shift(), horiz);
			while (sum.length) {
				if (operand) {
					num = convertCSS($el, sum.shift(), horiz);
					if (operand === "+") {
						val += num;
					} else if (operand === "-") {
						val -= num;
					} else if (operand === "*") {
						val *= num;
					} else if (operand === "/") {
						val /= num;
					}
					operand = "";
				} else {
					operand = sum.shift();
				}
			}
			break;
		case "em":
			val *= parseFloat($el.css("fontSize"));
			break;
		case "percent":
			val *= $el.offsetParent()[horiz ? "width" : "height"]() / 100;
			break
		case "rem":
			val *= parseFloat($("html").css("fontSize"));
			break;
		case "vh":
			val *= window.innerHeight / 100;
			break;
		case "vw":
			val *= window.innerWidth / 100;
			break;
		case "vmin":
			val *= Math.min(window.innerWidth, window.innerHeight) / 100;
			break;
		case "vmax":
			val *= Math.max(window.innerWidth, window.innerHeight) / 100;
			break;
		case "px":
		case "":
			break;
		default:
			console.warn("convertCSS: Unknown conversion type!! (" + value + ")");
	}
//	console.log("=", val);
	return value;
}