How to get hex integer from a string in JS?

Question

I would like to convert this: "#FFFFFF" to this: 0xFFFFFF. How is it possible without using eval?

Thanks in advance,

I am *sure* this is a duplicate... I wish the "related questions" were smarter about language tags :-/ — , Apr 23 '12 at 21:19
@ Danny: By "hex value," do you mean the **numeric** value FFFFFF hex (e.g., 16777215 decimal?). If so, just say "numeric value," putting the word "hex" in takes us into string land. I think you probably meant numeric, though. — T.J. Crowder, Apr 23 '12 at 21:28
I have just answered a similar question here: https://stackoverflow.com/questions/48140695/best-way-to-convert-hex-string-with-hash-to-hex-value-with-0x-in-javascript/70607982#70607982 — 8urning8eard, Jan 06 '22 at 13:43

score 59 · Accepted Answer · edited Jun 13 '19 at 00:37

59

Strip off the "#" and use parseInt().

var hex = parseInt(str.replace(/^#/, ''), 16);

Then, if you want to see it in hex, you can use .toString():

console.log(hex.toString(16));

edited Jun 13 '19 at 00:37

Mike 'Pomax' Kamermans

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answered Apr 23 '12 at 21:17

Pointy

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I would prefer `substring()` (as in @TJCrowder's answer) over `replace()`, for efficiency's sake. – Mark Reed Apr 23 '12 at 21:21
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@MarkReed: It totally depends on what the OP *really* wants, which isn't clear from the question. It may be (given the lack of quotes on `0xFFFFFF`) that the OP wants then numeric value (which, of course, would make the title of the question completely wrong -- not the first time!). – T.J. Crowder Apr 23 '12 at 21:22
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@TJCrowder: Your reply seems to be on the wrong answer. :) All I said above was that I would use `substring(1)` instead of `replace(regex)` for this problem. – Mark Reed Apr 23 '12 at 22:45
@Displee yes it does? – Pointy Aug 16 '17 at 22:46
@Pointy parseInt("#797e61".replace(/^#/, ''), 16); gives me 7962209 as result, and not 0x797e61. – Displee Aug 17 '17 at 00:25
@Displee of course, because the normal way to display numbers is in base 10, not base 16. – Pointy Aug 17 '17 at 00:35

score 0 · Answer 2 · answered Mar 10 '20 at 02:57

Use this code:

var resultP = document.getElementById('result');
var btn = document.querySelector('button');
var input = document.querySelector('input');
function convert(hex) {
  return Number(`0x${hex.substr(1)}`);
}
btn.addEventListener('click', () => {
  resultP.innerHTML = convert(input.value);
})

* {
  font-family: Arial;
}

<!DOCTYPE html>
<html>
  <head>
    <title>Hex code to hex integer</title>
    <meta charset="UTF-8" />
  </head>
  <body>
    <input type="text" maxlength="7" />
    <button>Done</button>
    <br />
    Result:
    <p id="result"></p>
  </body>
</html>

It's desirable that you give a brief explanation how the code solves the problem in the question. — bad_coder, Mar 10 '20 at 03:17

Sam Mulqueen · Answer 3 · 2023-04-16T03:30:02.633

You could try this code:

function hex2num(hexcode){ return Number(  '0x' + hexcode.split(/[^0-9a-fA-F]+/).join('')  ) }

This function will strip out all characters that are not numbers between 0-9 or alphabetical characters between A-F before trying to parse the input. The output is a number, because 0x009 === 9 in JS.

This solution works when dealing with numbers that are less than the MAX SAFE INTEGER (9007199254740991) but if the hex code equates to a number larger than that you will probably need to use a different solution.

Expected Usage:

hex2num('#0000FF') === 255 // true

hex2num('#FFFFFF') === 16777215 // true

hex2num('0x000000000001') === 1 // true

hex2num('0L0L4') === 4 // true

How to get hex integer from a string in JS?

3 Answers3