Jquery price formatting

var format = function(num){
	var str = num.toString().replace("$", ""), parts = false, output = [], i = 1, formatted = null;
	if(str.indexOf(".") > 0) {
		parts = str.split(".");
		str = parts[0];
	}
	str = str.split("").reverse();
	for(var j = 0, len = str.length; j < len; j++) {
		if(str[j] != ",") {
			output.push(str[j]);
			if(i%3 == 0 && j < (len - 1)) {
				output.push("");
			}
			i++;
		}
	}
	formatted = output.reverse().join("");
	return( formatted + ((parts) ? "." + parts[1].substr(0, 2) : ""));
};
$(function(){
    $("#currency").keyup(function(e){
        $(this).val(format($(this).val()));
    });
});