JSFiddle - React, Tailwind, and code Playground

JavaScript

var CHAR_SETS = {
    d: '0123456789',
    A: 'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
    w: '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
};

function mapString(s, func) {
    return Array.prototype.map.call(s, func).join('')
}

function randChar(charType) {
    var chars = CHAR_SETS[charType];
    if (chars) {
        return chars.charAt(parseInt(Math.random() * chars.length));
    } else {
        return charType;
    }
}

console.log(mapString('Add-wwww-AAA-ddA', randChar));