Credit Card Validation similar to the Luhn Algorithm

README.md

Validates a credit card number based on the information given at

http://www.mint.com/blog/trends/credit-card-code-01202011/

// Decreased from 139 to 124 chars =) // Also, now supports string coercion

function validCard(a,b,c,d){a+='';c=0;for(b=a.length;b--;){d=b%2?a[b]:a[b]*2;if(d>9)d=0|d/10+d%10;c+=+d}return c===c&&!c%10}

validCard('No Way I'm Putting Mine Here!!!') // returns true or false

// When testing, doesn't seem to work for any of my cards but neither did the algorithm I forked from. Oh well =/

annotated.js

function(
	a, //credit card number
	b, //placeholder
	c, //placeholder
	d //placeholder
	) {
		/*
			Validates according to algorithm given here:
			http://www.mint.com/blog/trends/credit-card-code-01202011/
		*/
		
		a+=''; //splits and reverses the credit card number
		c=0;
		
		//loops through each digit in credit card number
		for(b=a.length;b--;){
			d=b%2?a[b]:a[b]*2; // doubles every second number from right thanks to reversing of number
			//if double digits, split and add digits together
			if(d>9)
				d=0|d/10+d%10;
			
			c+=+d //total up
		} 
	return !c%10 //return valid if divisible by 10
}

index.js

function validCard(a,b,c,d){a+='';c=0;for(b=a.length;b--;){d=b%2?a[b]:a[b]*2;if(d>9)d=0|d/10+d%10;c+=+d}return c===c&&!c%10}

LICENSE.txt

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2011 Will McKenzie<www.oinutter.co.uk>

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. You just DO WHAT THE FUCK YOU WANT TO.

package.json

{
  "name": "creditCardValidation",
  "description": "Validates a credit card.",
  "keywords": [
    "creditcard",
    "validation",
    "form",
	"checksum"
  ]
}

Updated re: https://gist.github.com/993370#gistcomment-60299