26 lines
788 B
Markdown
26 lines
788 B
Markdown
### luhnCheck
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Implementation of the [Luhn Algorithm](https://en.wikipedia.org/wiki/Luhn_algorithm) used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers etc.
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Works with numbers and strings alike
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``` js
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const luhnCheck = num => {
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let arr = (num+'').split('').reverse()
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let lastDigit = arr.splice(0,1)
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let sum = arr.reduce((acc,val,i) => {
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val = parseInt(val)
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if(i%2!==0) return acc + val
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else{
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val = (val * 2)%9 || 9
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return acc+ val }
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},0)
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sum += parseInt(lastDigit)
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return sum%10 === 0
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}
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```
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```js
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luhnCheck("4485275742308327"); //true
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luhnCheck(4485275742308327); //true
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luhnCheck(6011329933655299); // true
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luhnCheck(123456789); //false
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```
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