A credit card validation function using the Luhn algorithm.
Inspiration for this came from: https://www.mint.com/blog/trends/credit-card-code-01202011/
Test credit card data from: https://www.paypalobjects.com/en_US/vhelp/paypalmanager_help/credit_card_numbers.htm.
| function( | |
| c, // credit card number to validate | |
| a, // length of credit card (placeholder) | |
| r, // sum of digits (for Luhn algorithm) (placeholder) | |
| d, // current digit (placeholder) | |
| x // counter (placeholder) | |
| ){ | |
| for( | |
| a = c.length, // get the card's length | |
| x = r = 0; // initialize counter and sum | |
| a--; // work through the string backwards | |
| ) | |
| d = +c[a], // convert current digit to integer | |
| r += // sum for Luhn algorithm.. | |
| x % 2 ? // if the counter is even or 0.. | |
| d < 5 ? // if the current digit is less than 5 | |
| // (a.k.a. multiplying digit by two will | |
| // result in a single digit product) | |
| d * 2 // add the current digit times 2 to the sum | |
| : // else | |
| d * 2 - 9 // add the current digit times 2 minus 9 | |
| : // else | |
| d, // add the current digit to the sum | |
| x++; // increment counter | |
| return!(r%10) // return true if sum % 10 is 0 | |
| } |
| function(c,a,r,d,x){for(a=c.length,x=r=0;a--;)d=+c[a],r+=x%2?d<5?d*2:d*2-9:d,x++;return!(r%10)} |
| DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE | |
| Version 2, December 2004 | |
| Copyright (C) 2011 YOUR_NAME_HERE <YOUR_URL_HERE> | |
| 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. |
| { | |
| "name": "creditCardValidator", | |
| "description": "A credit card validation function using the Luhn algorithm.", | |
| "keywords": [ | |
| "creditcard", | |
| "validation", | |
| "luhn" | |
| ] | |
| } |
| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <title>140byt.es Credit Card Validation Test</title> | |
| <style type="text/css"> | |
| th,td { padding: 5px 10px } | |
| </style> | |
| </head> | |
| <body> | |
| <table border="1"> | |
| <thead> | |
| <tr> | |
| <th>CreditCard</th> | |
| <th>Expected</th> | |
| <th>Actual</th> | |
| </tr> | |
| </thead> | |
| <tbody> | |
| <tr> | |
| <td>378282246310005</td> | |
| <td>true</td> | |
| <td id="cc0"></td> | |
| </tr> | |
| <tr> | |
| <td>371449635398431</td> | |
| <td>true</td> | |
| <td id="cc1"></td> | |
| </tr> | |
| <tr> | |
| <td>378734493671000</td> | |
| <td>true</td> | |
| <td id="cc2"></td> | |
| </tr> | |
| <tr> | |
| <td>30569309025904</td> | |
| <td>true</td> | |
| <td id="cc3"></td> | |
| </tr> | |
| <tr> | |
| <td>38520000023237</td> | |
| <td>true</td> | |
| <td id="cc4"></td> | |
| </tr> | |
| <tr> | |
| <td>6011111111111117</td> | |
| <td>true</td> | |
| <td id="cc5"></td> | |
| </tr> | |
| <tr> | |
| <td>6011000990139424</td> | |
| <td>true</td> | |
| <td id="cc6"></td> | |
| </tr> | |
| <tr> | |
| <td>5555555555554444</td> | |
| <td>true</td> | |
| <td id="cc7"></td> | |
| </tr> | |
| <tr> | |
| <td>5105105105105100</td> | |
| <td>true</td> | |
| <td id="cc8"></td> | |
| </tr> | |
| <tr> | |
| <td>4111111111111111</td> | |
| <td>true</td> | |
| <td id="cc9"></td> | |
| </tr> | |
| <tr> | |
| <td>4012888888881881</td> | |
| <td>true</td> | |
| <td id="cc10"></td> | |
| </tr> | |
| <tr> | |
| <td>4222222222222</td> | |
| <td>true</td> | |
| <td id="cc11"></td> | |
| </tr> | |
| <tr> | |
| <td>378282246310006</td> | |
| <td>false</td> | |
| <td id="cc12"></td> | |
| </tr> | |
| <tr> | |
| <td>371449635398439</td> | |
| <td>false</td> | |
| <td id="cc13"></td> | |
| </tr> | |
| <tr> | |
| <td>378734493671005</td> | |
| <td>false</td> | |
| <td id="cc14"></td> | |
| </tr> | |
| <tr> | |
| <td>4111111111111112</td> | |
| <td>false</td> | |
| <td id="cc15"></td> | |
| </tr> | |
| </tbody> | |
| </table> | |
| <script> | |
| var v = function(c,a,r,d,x){for(a=c.length,x=r=0;a--;)d=+c[a],r+=x%2?d<5?d*2:d*2-9:d,x++;return!(r%10)}; | |
| var cards = ["378282246310005", // Valid | |
| "371449635398431", | |
| "378734493671000", | |
| "30569309025904", | |
| "38520000023237", | |
| "6011111111111117", | |
| "6011000990139424", | |
| "5555555555554444", | |
| "5105105105105100", | |
| "4111111111111111", | |
| "4012888888881881", | |
| "4222222222222", | |
| "378282246310006", // Invalid | |
| "371449635398439", | |
| "378734493671005", | |
| "4111111111111112"]; | |
| for (var i=0; i < cards.length; i++) { | |
| var result = v(cards[i]); | |
| document.getElementById("cc" + i).innerHTML = result; | |
| } | |
| </script> | |
| </body> | |
| </html> |