Strings and RegExp 1. Binary Decoding

function solve() {
    let input = document.getElementById("input").value;
    let sum = calculateSum(input);
    let result = document.getElementById('resultOutput');

    function calculateSum(input) {
        return input
            .split('')
            .map(Number)
            .reduce((a, b) => a + b);
    }
    if (String(sum).length > 1) {
        while (String(sum).length > 1) {
            sum = String(sum)
                .split('')
                .map(Number)
                .reduce((a, b) => a + b);
        }
    }
    result.innerHTML = input
        .substring(sum, input.length - sum)
        .match(new RegExp('.'.repeat(8), "gim"))
        .map(e => parseInt(e, 2))
        .map(e => String.fromCharCode(e)).join('');
    return result;
}