JS function to convert RGB color values ​​into HTML hexadecimal (HEX) code_javascript skills

//Go to fixed-length hexadecimal characters string, if not enough, fill in 0
function zero_fill_hex(num, digits) {
var s = num.toString(16);
while (s.length < digits)
s = "0" s;
return s;
}

//Damn it, I couldn’t find how to use javascript to find the value of a background color, so I had to parse it myself
function rgb2hex(rgb) {
//nnd, Firefox / IE not the same, fxck
if (rgb.charAt(0) == '#')
return rgb;
var n = Number(rgb);
var ds = rgb.split(/D /);
var decimal = Number(ds[1]) * 65536 Number(ds[2]) * 256 Number(ds[3]);
return "#" zero_fill_hex(decimal, 6);
}