Simple Module Pattern

Use an IFFE (immediately invoked function expression) that gets invoked immediately and emulates an block scope (like let in ES6) for you.

yourmodule.js

(function(global, undefined) {
    // insert your code here
    // global is window in the browser and global in node.js
}(this));

backbone style:

(function() {
    // insert your code here
}).call(this);