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Luhn validation algorithm
* Luhn algorithm in JavaScript: validate credit card number supplied as string of numbers
* @author ShirtlessKirk. Copyright (c) 2012.
* @license WTFPL (
var luhnChk = (function (arr) {
return function (ccNum) {
len = ccNum.length,
bit = 1,
sum = 0,
while (len) {
val = parseInt(ccNum.charAt(--len), 10);
sum += (bit ^= 1) ? arr[val] : val;
return sum && sum % 10 === 0;
}([0, 2, 4, 6, 8, 1, 3, 5, 7, 9]));

ShirtlessKirk commented Mar 20, 2012

Closure compiled version (updated Feb 11, 2015):

var luhnChk=function(a){return function(c){for(var l=c.length,b=1,s=0,v;l;)v=parseInt(c.charAt(--l),10),s+=(b^=1)?a[v]:v;return s&&0===s%10}}([0,2,4,6,8,1,3,5,7,9]);

parris commented Sep 24, 2012

This is awesome and apparently the most performant luhncheck in js (in chrome at least). Not sure if you have seen this:

ondrek commented Oct 14, 2013

wow! awesome! not only fast, but also beautiful code <3
thank you, dude


Woww! So far the Fastest Algorithm i've tried! 👍

oPorks commented Jul 28, 2014

Well done!

lagden commented Aug 14, 2014

Fuckk Yeahhh!!!


ShirtlessKirk commented Feb 11, 2015

Spot of code golf: After reviewing subsequent edits on jsperf, I've tweaked the code. The test case is at if you want to check.

  • decrement now happens inline rather than during the while conditional check (I prefer that placement)
  • reduction of product array contents to just the doubled number value as you've already got the undoubled value (less to initialise, less to look up)
  • the use of a closure to use the product array as a parameter was intriguing
  • return statement reversed to utilise short-circuiting better (if a zero length string is sent in then the sum is 0, cosmetic really)

A variant on the jsperf page doesn't run parseInt() if using the undoubled value. Personally, I don't like using it in some places and not others so I always run it. That's why this code isn't the fastest...

Ummm, WOW. TY!!!!

I am new, any one can tell me how can i use this code?
I want to validate cards.
and this code can validate all type of cards?

lebiru commented May 14, 2015

+1 thanks!

alesch commented May 25, 2015

@geniuscarpi: Use it as luhnChk("numberToValidate").

tomByrer commented Aug 6, 2015

I'm a bit confused the reason for bit ^= 1, since it seems that bit never changes? (version Feb 11, 2015)

jlukic commented Aug 13, 2015

Using an adapted version of your luhn check in our validation

Hey, I passed a test with 7 digits 2222222. Isn't valid credit card has digits range from 12 to 19? is this a bug?


ShirtlessKirk commented Oct 27, 2015

@tomByrer: yeah it does. ^= flips the value. It's a bitwise operator, not a Boolean one (see MDN page)

@celerycup: this is just a Luhn algorithm (see Wikipedia). Apart from checking for zero length strings there is no range checking as that is outside the scope of the method and checking for credit card number validity is just one application of it. For example, you could set up a login verification solution using identifier numbers that must pass Luhn to be valid.

thensg commented Nov 2, 2015

I decided to adapt your code, but add support for creating a Luhn checksum. You can find the changes here:

MasterCard announced new bin ranges (222100 - 272099) in November 2014, and will be introduced into the payment eco-system on October 2016, not sure if this validates them, but I'm assuming it will.

enapupe commented Dec 2, 2015

There is a small issue regarding user input. The input MUST be a string, otherwise the return is always 0


ShirtlessKirk commented Mar 18, 2016

@enapupe: well, yeah. Credit card numbers aren't actual integers but a string of integers; every Luhn implementation expects a string to work with. Not only that, line 2 even says so...
As for returning 0, that's a falsey value, so the function still "works" ;)

Wow, Impressive

The luhn test is failing for the MasterCard BIN 2-Series (222100-272099)

Sample Master Card:
2221 0012 3412 3456,
Expiry : 12/18


ShirtlessKirk commented Oct 11, 2016

@afixibiranchi I see that your issue was answered on . I'm guessing you used the "number" on the example card image of where it would make sense to be an invalid number...

heymartinadams commented Sep 29, 2017

Wonderful! Thank you.

eugene-chernogradski commented Oct 26, 2017

@ShirtlessKirk OMFG
Phil, dude, who could've imagined it'would be your implementation of Luhn check I'm gonna use?!

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