maettig · February 3, 2012 16:02 · maettig · Feb 7, 2012 · tsaniel · Feb 9, 2012
diff --git a/README.md b/README.md
diff --git a/annotated.js b/annotated.js
 function(a)
 {
  for (var b = /\d/g,             //initialize regular expression to match single digits
    c = 0,                        //initialize checksum
    d,
    e = 25;                       //should be 25 - 13 * 2 = -1 in the end, so `~e` is 0
    d = b.exec(a);                //fetch a single digit from the input
    e -= 2)
    c += e % 4 * d;               //multiply current digit with 3, 1, 3, 1 and so on
  return !(~e | c % 10)           //e must be -1 and sum must be 0
 }
diff --git a/index.js b/index.js
 function(a){for(var b=/\d/g,c=0,d,e=25;d=b.exec(a);e-=2)c+=e%4*d;return!(~e|c%10)}
diff --git a/LICENSE.txt b/LICENSE.txt
            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2012 Thiemo Mättig <http://maettig.com>

 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.
diff --git a/package.json b/package.json
 {
  "name": "isValidEan13",

  "description": "Validate EAN-13 and ISBN-13 Numbers.",

  "keywords": [
    "checksum",
    "ean",
    "isbn",
    "validation"
  ]
 }
diff --git a/test.html b/test.html
 <!DOCTYPE html>
 <ul>
 <script type="text/javascript">
 // 82 bytes
 var isValidEan13 = function(a)
 {
  for (var b = /\d/g,             //initialize regular expression to match single digits
    c = 0,                        //initialize checksum
    d,
    e = 25;                       //should be 25 - 13 * 2 = -1 in the end, so `~e` is 0
    d = b.exec(a);                //fetch a single digit from the input
    e -= 2)
    c += e % 4 * d;               //multiply current digit with 3, 1, 3, 1 and so on
  return !(~e | c % 10)           //e must be -1 and sum must be 0
 }
 // 126 bytes
 var formatEan13 = function(a, b, c)
 {
  for (a = ('' + a)               //force `a` to be a string
    .split(/\D*/)                 //split into digits, remove all non-digits
      .slice(0, b = 12),          //use the first 12 digits only
    c = 9;                        //this makes the final calculation easier, -1 also works
    b--;
    a[12] = 9 - c % 10)           //append or replace checksum
    c += (b * 2 & 2 | 1) *        //multiply current digit with 3, 1, 3, 1 and so on
      (a[b] += b % 6 ? '' : ' '); //format with spaces
  return a.join('')               //array to string
 }
 var tests = ['5 449000 096241', '5 901234 123457', 9783161484100,
  '5 449000 096242', 9783161484105, 413456789018, 41345678901800, 413456789018000];
 for (var i = 0; i < tests.length; i++)
 {
  var v = isValidEan13(tests[i]);
  var e = formatEan13(tests[i]);
  document.write('<li>EAN/ISBN ' +
    (v ? '<var>' + tests[i] + '</var>' : '<b>' + tests[i] + '</b>') +
    ' (a ' + typeof tests[i] + ') is ' +
    (v ? '' : 'in') + 'valid. Should be <var>' + e + '</var>.');
 }
 </script>
 </ul>
	function(a)
	{
	for (var b = /\d/g, //initialize regular expression to match single digits
	c = 0, //initialize checksum
	d,
	e = 25; //should be 25 - 13 * 2 = -1 in the end, so `~e` is 0
	d = b.exec(a); //fetch a single digit from the input
	e -= 2)
	c += e % 4 * d; //multiply current digit with 3, 1, 3, 1 and so on
	return !(~e \| c % 10) //e must be -1 and sum must be 0
	}
	DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
	Version 2, December 2004

	Copyright (C) 2012 Thiemo Mättig <http://maettig.com>

	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": "isValidEan13",

	"description": "Validate EAN-13 and ISBN-13 Numbers.",

	"keywords": [
	"checksum",
	"ean",
	"isbn",
	"validation"
	]
	}
	<!DOCTYPE html>
	<ul>
	<script type="text/javascript">
	// 82 bytes
	var isValidEan13 = function(a)
	{
	for (var b = /\d/g, //initialize regular expression to match single digits
	c = 0, //initialize checksum
	d,
	e = 25; //should be 25 - 13 * 2 = -1 in the end, so `~e` is 0
	d = b.exec(a); //fetch a single digit from the input
	e -= 2)
	c += e % 4 * d; //multiply current digit with 3, 1, 3, 1 and so on
	return !(~e \| c % 10) //e must be -1 and sum must be 0
	}
	// 126 bytes
	var formatEan13 = function(a, b, c)
	{
	for (a = ('' + a) //force `a` to be a string
	.split(/\D*/) //split into digits, remove all non-digits
	.slice(0, b = 12), //use the first 12 digits only
	c = 9; //this makes the final calculation easier, -1 also works
	b--;
	a[12] = 9 - c % 10) //append or replace checksum
	c += (b * 2 & 2 \| 1) * //multiply current digit with 3, 1, 3, 1 and so on
	(a[b] += b % 6 ? '' : ' '); //format with spaces
	return a.join('') //array to string
	}
	var tests = ['5 449000 096241', '5 901234 123457', 9783161484100,
	'5 449000 096242', 9783161484105, 413456789018, 41345678901800, 413456789018000];
	for (var i = 0; i < tests.length; i++)
	{
	var v = isValidEan13(tests[i]);
	var e = formatEan13(tests[i]);
	document.write('<li>EAN/ISBN ' +
	(v ? '<var>' + tests[i] + '</var>' : '<b>' + tests[i] + '</b>') +
	' (a ' + typeof tests[i] + ') is ' +
	(v ? '' : 'in') + 'valid. Should be <var>' + e + '</var>.');
	}
	</script>
	</ul>