toString(16) with leading zeroes

Question

When you convert a small number to a hexadecimal representation, you need leading zeroes, because toString(16) will return f for 15, instead of 00000f. Usually I will use the loop like this:

var s = X.toString(16); while (s.length < 6) s = '0' + s

is there a better way in JavaScript?

UPD: The answer suggested answer How can I create a Zerofilled value using JavaScript? is not what I am looking for, I look for a very short code, that is suited specifically for 24 bit integers converted to a hexadecimal looking strings.

that answer is 8 lines of code! I am looking for something that is shorter than my ONE line — exebook, Jan 28 '14 at 14:52
@exebook: It depends whether you need to support arbitrary-long fills, decimals, negative numbers… You can extract a useful oneliner from the answers. — Bergi, Jan 28 '14 at 14:55
Similar question: [Javascript add leading zeroes to date](http://stackoverflow.com/q/3605214/3096782) — cookie monster, Jan 28 '14 at 14:59

score 4 · Accepted Answer · edited Jan 30 '14 at 08:25

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How about

('00000'+(15).toString(16)).substr(-5)

edited Jan 30 '14 at 08:25

exebook

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answered Jan 28 '14 at 14:44

CBroe

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That is interesting +1 – epascarello Jan 28 '14 at 14:46
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-1: [`substr`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substr) with negative indizes is not supported by IE. Use `slice` instead. – Bergi Jan 28 '14 at 14:51
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Also OP is looking to pad a number **`X`** to a length of **`6`**… – Bergi Jan 28 '14 at 14:56
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Cool, but ridiculous. There has to be a better way. – jdbertron Sep 26 '22 at 16:51

score 0 · Answer 2 · answered Jan 28 '14 at 14:44

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Maybe this:

var s = X.toString(16);
s = "000000".substr(0, 6 - s.length) + s;

answered Jan 28 '14 at 14:44

user3146587

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toString(16) with leading zeroes

2 Answers2