Step 12
Here is the completed Luhn algorithm:
You can try the above for another valid input, 6011329933655299
.
Now you can complete the starter code by providing an implementation for the isCardNumberValid
function:
function isCardNumberValid(cnumber) {
let arr = cnumber
.split("")
.reverse()
.map((element) => parseInt(element));
const sum = arr.reduce(reducer, 0);
function reducer(accumulator, currentValue, currentIndex) {
currentIndex += 1; // account for 0-based indexing
if (currentIndex % 2 === 0) {
// even index
currentValue *= 2;
if (currentValue > 9) {
currentValue -= 9;
}
}
return accumulator + currentValue;
}
return sum % 10 === 0;
}
Here is the payment form in action: