This pattern is commonly used when using the same namespace object across multiple files. By putting
var page = page || {};
at the top of each file that touches that namespace, you're guaranteed that page
will point to the same object, and you can load them in any order, if your code permits.
// page1.js
var page = page || {};
page.doSomething = function() {};
// page2.js
var page = page || {}
page.doSomethingElse = function() {};
// page3.js
var page = page || {};
page.doThirdThing = function() {};