Replace all chars with #, except for last 4

Question

function maskify(cc) {
    var dd = cc.toString();
    var hash = dd.replace((/./g), '#');
    for (var i = (hash.length - 4); i < hash.length; i++) {
        hash[i] = dd[i];
    }
    return hash;
}

I am trying to replace all chars with # except for last 4. Why isn't it working?

Answer 1

You could do it like this:

dd.replace(/.(?=.{4,}$)/g, '#');

var dd = 'Hello dude';
var replaced = dd.replace(/.(?=.{4,}$)/g, '#');
document.write(replaced);

Answer 2

If you find the solution, try this trick

function maskify(cc) {
  return cc.slice(0, -4).replace(/./g, '#') + cc.slice(-4);
}