hillerstorm/LICENSE.txt

## README.md

      
    Raw
  

              README.md
            
          
    Calculate checksum using the Luhn Algorithm

Calculates the checksum of a given input of numbers using the Luhn Algorithm
75bytes

  
## annotated.js
function(
    a,  // input number sequence as a string
    b,  // placeholder
    c,  // --||--
    d){ // --||--
    c=0;
    // traverse the input and multiply every other digit
    for(b in a)
        d=a[b],c+=
            b%2?+d       // every other digit is just used straight away
            :d*2%10|d/5; // digits above 5 will result in double digits when
                         // multiplied with 2 and should be added together
                         //
                         // 5*2 = 10 -> 1+0 = 1
                         // 6*2 = 12 -> 1+2 = 3
                         // 7*2 = 14 -> 1+4 = 5
                         // 8*2 = 16 -> 1+6 = 7
                         // 9*2 = 18 -> 1+8 = 9
                         //
                         // digits below 5 are just multiplied by 2
                         // and this, is magic

    // multiply the sum by 9 and return the last digit
    return c*9%10
}

## index.js
function(a,b,c,d){c=0;for(b in a)d=a[b],c+=b%2?+d:d*2%10|d/5;return c*9%10}

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

 Copyright (C) 2013 Johan Hillerström <https://github.com/hillerstorm>

 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": "luhnAlgorithm",

  "description": "Calculates a checksum using the Luhn algorithm.",

  "keywords": [
    "luhn",
    "algorithm",
    "formula",
    "checksum"
  ]
}

## test.html
<!DOCTYPE html>
<title>Foo</title>
<div>Expected value: <b>6</b></div>
<div>Actual value: <b id="ret"></b></div>
<script>
  var luhn = function(a,b,c,d){c=0;for(b in a)d=a[b],c+=b%2?+d:d*2%10|d/5;return c*9%10}

  document.getElementById('ret').innerHTML = luhn('811218987')
</script>
	function(
	a, // input number sequence as a string
	b, // placeholder
	c, // --\|\|--
	d){ // --\|\|--
	c=0;
	// traverse the input and multiply every other digit
	for(b in a)
	d=a[b],c+=
	b%2?+d // every other digit is just used straight away
	:d*2%10\|d/5; // digits above 5 will result in double digits when
	// multiplied with 2 and should be added together
	//
	// 5*2 = 10 -> 1+0 = 1
	// 6*2 = 12 -> 1+2 = 3
	// 7*2 = 14 -> 1+4 = 5
	// 8*2 = 16 -> 1+6 = 7
	// 9*2 = 18 -> 1+8 = 9
	//
	// digits below 5 are just multiplied by 2
	// and this, is magic

	// multiply the sum by 9 and return the last digit
	return c*9%10
	}
	DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
	Version 2, December 2004

	Copyright (C) 2013 Johan Hillerström <https://github.com/hillerstorm>

	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": "luhnAlgorithm",

	"description": "Calculates a checksum using the Luhn algorithm.",

	"keywords": [
	"luhn",
	"algorithm",
	"formula",
	"checksum"
	]
	}
	<!DOCTYPE html>
	<title>Foo</title>
	<div>Expected value: <b>6</b></div>
	<div>Actual value: <b id="ret"></b></div>
	<script>
	var luhn = function(a,b,c,d){c=0;for(b in a)d=a[b],c+=b%2?+d:d2%10\|d/5;return c9%10}

	document.getElementById('ret').innerHTML = luhn('811218987')
	</script>