xxxxxxxxxx
function luhnChk(num) {
let array = (num + '').split('').reverse().map(x => parseInt(x));
let theLastDig = array.shift();
let sum = array.reduce((prevVal, curVal, index) => (index % 2 !== 0 ? prevVal + curVal : prevVal + ((curVal *= 2) > 9 ? curVal - 9 : curVal)), 0);
sum += theLastDig;
return sum % 10 === 0;
}
xxxxxxxxxx
const luhnCheck = num => {
const arr = (num + '')
.split('')
.reverse()
.map(x => parseInt(x));
const lastDigit = arr.shift();
let sum = arr.reduce(
(acc, val, i) => (i % 2 !== 0 ? acc + val : acc + ((val *= 2) > 9 ? val - 9 : val)),
0
);
sum += lastDigit;
return sum % 10 === 0;
};
luhnCheck('4485275742308327'); // true
luhnCheck(6011329933655299); // true
luhnCheck(123456789); // false
xxxxxxxxxx
const luhnCheck = num => {
const arr = (num + '')
.split('')
.reverse()
.map(x => parseInt(x));
const lastDigit = arr.shift();
let sum = arr.reduce(
(acc, val, i) => (i % 2 !== 0 ? acc + val : acc + ((val *= 2) > 9 ? val - 9 : val)),
0
);
sum += lastDigit;
return sum % 10 === 0;
};