JSFiddle - React, Tailwind, and code Playground

JavaScript

// moduleA.js
    
var MyApplication = (function(app) {
    
    app.util = app.util || {};

    app.util.hypotenuse = function(a, b) {
        return Math.sqrt(a * a + b * b);
    };

    return app;
})(MyApplication || {});

// ----------

// moduleB.js

var MyApplication = (function(app) {
    
    app.util = app.util || {};

    app.util.area = function(a, b) {
        return a * b / 2;
    };

    return app;
})(MyApplication || {});

// ----------

// index.js - here you have to include both moduleA and moduleB manually
// or write some loader

var a = 3,
    b = 4;
console.log('Hypotenuse: ', MyApplication.util.hypotenuse(a, b));
console.log('Area: ', MyApplication.util.area(a, b));