08. Hard Word

function hardWord(letter) {
    let pattern = /[_]{1,}/g;
    let string = letter[0]
    let output = letter[0];

    while ((word = pattern.exec(string)) !== null) {
        letter[1].forEach(element => {
            if (element.length === word[0].length) {
                output = output.substr(0, word.index) + element + output.substr(word.index + element.length);
            }
        });
    }
    console.log(output);
}