将字符串转换为十六进制，然后返回字符串

Question

I have to convert a working C# function to JavaScript so it executes client-side. Here's the C#...

// convert the cmac into a hex number so we can increment it and get the emac
long emacLong = Convert.ToInt64(_cmac, 16) + 1;
emac = emacLong.ToString("x12").ToUpper();

Here's what I have so far in JavaScript..

var emac = parseInt(cmac, 16) + 1;
emac = emac.toString(16);

The input is "0015D1833339". The output should be "0015D183333A". However, the JavaScript returns "15d183333a". I need to retain the leading 0's. Looks like the C# function accomplishes this with the "x12" parameter of .ToString. How do I accomplish this in JavaScript? I need to convert it to an integer, increment it by 1 and then convert back to a string with a length of 12 characters.

Answer 1

Easy way to pad hex number output when you know the exact length you desire is with something like this:

var emac = parseInt(cmac, 16) + 1;
emac = ("000000000000" + emac.toString(16)).substr(-12);

// or if you MUST have all caps....
emac = ("000000000000" + emac.toString(16)).substr(-12).toUpperCase();

This example is for length 12, if you need a different length, you would adjust the length of the 0 string and the substr param.