JSFiddle - React, Tailwind, and code Playground

by qwertynl

JavaScript

function multiplyby11(number) {
    var num = number + "";
    var integers = num.split('');
    var numbers = [];
    integers.forEach(function (val) {
        numbers.push(parseInt(val));
    });
    var multiply = [];
    multiply.push(numbers[0]);
    var number_length = numbers.length;
    for (var i = 1; i < number_length; ++i) {
        multiply.push(numbers[i] + numbers[i - 1])
    }
    multiply.push(numbers[number_length - 1]);

    function removeAllMultiplesOfTen() {
        var allRemoved = true;
        multiply.forEach(function (val, index) {
            if (val >= 10) {
                val -= 10;
                multiply[index - 1]++;
                multiply[index] = val;
                allRemoved = false;
            }
        });
        if (!allRemoved) {
            removeAllMultiplesOfTen();
        }
    }

    removeAllMultiplesOfTen();
    return multiply.join('');
}

var mult = multiplyby11(15487548796454858);
console.log(mult);