Question

Lets assume modulex and moduley both are not declared at all.
Now consider two scenarios:

var modulex = modulesx || {}; // This line of code works fine

moduley = moduley || {}; // but this code throws error saying moduley is undefined.

Again,

var modulex = moduley || {}; // This also throws error saying moduley is undefined.

Please elaborate on this one.

Answer 1

In JavaScript, variable declarations are hoisted. This code:

var a = a || {};

Is actually interpreted like this:

var a;
a = a || {};

In your second example, moduley just isn’t defined, which is exactly what your error says.