# JavaScript: Implement the Luhn Algorithm used to validate a variety of identification numbers

## JavaScript fundamental (ES6 Syntax): Exercise-80 with Solution

Write a JavaScript program to implement the Luhn Algorithm used to validate identification numbers. For example, credit card numbers, IMEI numbers, National Provider Identifier numbers etc.

• Use String.prototype.split(''), Array.prototype.reverse() and Array.prototype.map() in combination with parseInt() to obtain an array of digits.
• Use Array.prototype.splice(0, 1) to obtain the last digit.
• Use Array.prototype.reduce() to implement the Luhn Algorithm.
• Return true if sum is divisible by 10, false otherwise.

Sample Solution:

JavaScript Code:

``````//#Source https://bit.ly/2neWfJ2
const luhnCheck = num => {
let arr = (num + '')
.split('')
.reverse()
.map(x => parseInt(x));
let lastDigit = arr.splice(0, 1);
let sum = arr.reduce((acc, val, i) => (i % 2 !== 0 ? acc + val : acc + ((val * 2) % 9) || 9), 0);
sum += lastDigit;
return sum % 10 === 0;
};
console.log(luhnCheck('4485275742308327'));
console.log(luhnCheck(6011329933655299));
console.log(luhnCheck(123456789));
```
```

Sample Output:

```true
false
false
```

Flowchart: Live Demo:

See the Pen javascript-basic-exercise-80-1 by w3resource (@w3resource) on CodePen.

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