JSFiddle - React, Tailwind, and code Playground

JavaScript

window.namespace = { fun1: { fun2: { fun3: function() { alert('hi!') }}}};

runFunc = function(address) {
    var addressArray = address.split('.'),
        current = window,
        i = 0;
    
    for (i = 0; i < addressArray.length; i++) {
        current = current[addressArray[i]];
    }
    
    current();
};

runFunc('namespace.fun1.fun2.fun3');