27 lines
965 B
Markdown
27 lines
965 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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Use `String.split('')`, `Array.reverse()` and `Array.map()` in combination with `parseInt()` to obtain an array of digits.
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Use `Array.splice(0,1)` to obtain the last digit.
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Use `Array.reduce()` to implement the Luhn Algorithm.
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Return `true` if `sum` is divisible by `10`, `false` otherwise.
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``` js
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const luhnCheck = num => {
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let arr = (num+'').split('').reverse().map(x => parseInt(x));
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let lastDigit = arr.splice(0,1)[0];
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let sum = arr.reduce((acc,val,i) => i%2!==0 ? acc + val : acc + (val * 2) % 9 || 9,0);
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sum += 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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