I also attempted a fix with the other issue. 
Changed few lines to this:
_____________________________________________________________________

    for (let word of words) {
        if (idx > MAX_LENGTH) {
            newline += '\n';
            idx = 0;
        }
        newline += word + ' ';
        idx += word.length + 1; // Include the length of the space character
    }
_____________________________________________________________________

Well, our artificial "dev-san" did. I also got her to call me "Master"
during the process ヽ(´∇`)ノ