Query about OR operator while inititating a variable

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.

score 1 · Answer 1 · answered Jan 17 '13 at 07:09

1

You can't use variable which was not declared on the left side of "=" or as function parameter. Reference is not initialized.

answered Jan 17 '13 at 07:09

Damask

score 1 · Accepted Answer · answered Jan 17 '13 at 07:10

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.

answered Jan 17 '13 at 07:10

Blender

Then var a = a || {} doesnt make any sense.. because it would be as good as saying var a= {} ; Also even if a is undefined it should have been interpreted as false and should have taken the value after || operator... Isn't it? – Abhijeet Pawar Jan 17 '13 at 07:18
1

@AbhijeetPawar: Take a look at this: http://stackoverflow.com/questions/833661/what-is-the-difference-in-javascript-between-undefined-and-not-defined – Blender Jan 17 '13 at 07:21
Adding more to question... if I "declare" the same variable twice then the second declaration will have no effect at all... am I right? – Abhijeet Pawar Jan 17 '13 at 07:51
@AbhijeetPawar: Try it out. It doesn't do anything. – Blender Jan 17 '13 at 07:52

score 0 · Answer 3 · answered Jan 17 '13 at 07:11

0

Since your 'moduley' was not defined before using it, javascript compiler will call it as 'undefined'

answered Jan 17 '13 at 07:11

gurvinder372

3 Answers3