How can I convert an integer to hex with a fix length in Javascript?

Question

I want to convert an Integer to a hex-string with a fix length in JavaScript

For example I want to convert 154 to hex with a length of 4 digits (009A). I can't figure out a proper way to do that.

Answer 1

Number.prototype.toString() can convert a number to hexadecimal when 16 is passed as the argument (base 16):

new Number(154).toString(16) //'9A'

However, this will not have leading zeroes. If you wish to prepend the leading zeroes you can provide a string of 4 zeroes '0000' to concatenate with '9A', then use slice to grab just the last 4 characters:

var value = 154;
var hex = ('0000' + value.toString(16).toUpperCase()).slice(-4); //009A

The sequence of events is displayed like this:

154 -> '9a' -> '9A' -> '00009A' -> '009A'

Answer 2

You could add some zeroes and use String#slice for the stringed number.

var value = 154,
    string = ('0000' + value.toString(16).toUpperCase()).slice(-4);
    
console.log(string);

With String#padStart

var value = 154,
    string = value.toString(16).toUpperCase().padStart(4, 0);
    
console.log(string);