JSFiddle - React, Tailwind, and code Playground

JavaScript

function getSequence(template) {
    var r = '', ch, n;
    for (var i = 0; i < template.length; i++) {
        ch = template.substr(i, 1);
        if (ch == "n") {
            r += parseInt(Math.random() * 10);
        } else if (ch == "A") {
            r += String.fromCharCode(65 + parseInt(Math.random() * 26));
        } else if (ch == "e") {
            n = parseInt(Math.random() * 36);
            if (n > 9) {
                r += String.fromCharCode(55 + n);
            } else {
                r += n;
            }
        } else {
            r += ch;
        }
    }
    return r;
}
console.log(getSequence('Ann-eeee-AAA-nnA'));