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I have two part question about creating namespaces in JavaScript, which one of the following is proper/better way to define a namespace:

// style 1
var company = company || {};
company.models = company.models || {};
company.models.class = {...}

// style 2
company = typeof (company) == 'undefined' ? {} : company; 
company.models = company.models || {};
company.models.class = {...}

Please note there are TWO differences in the styles. First is use of typeof and Second is the style 2 does NOT use the var key.

Both these styles seem to work and now here is where it gets really confusing. If I remove the var key from style 1 then namespace does NOT work at all. I get something like company is not defined. I think it has something to do with the var creating a global variable and without var we are creating a global property as explained in here

What is the purpose of the var keyword and when to use it (or omit it)?

Would some please explain to me why the style 1 fails without the var key?

Many thanks in advance.

Community
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Farnam
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  • Perhaps you have 'use strict' enabled somewhere in scope? That would not permit creation of global variables/properties. – Billy Moon Feb 21 '15 at 00:45

1 Answers1

1

It's matter of likes but I prefer the first one since It is shorter and more readable.

First style 'means':

Create local variable 'company'. If it exists(and its value is not falsy) in an upper scope asign that to this variable else asign a new object.

Second one 'means'

Assign to company variable a new object if it is undefined or itself if it is defined.

The first one triggers a ReferenceError if you remove 'var' because the second reference (company = company) doesn't exists and the interpreter doesn't know how to deal with that. If it exists it will work even if you remove 'var'.

Another note for the first style is that company will be overwritten with a new object even if it is a falsy value like 0, null or ""

Mardie
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