Can anyone tell me what this javascript might be doing

Question

So I am looking over a project which includes the following line of javascript:

window.negotiationApp = window.negotiationApp || {};

Can anyone explain might be going on with this line of code?

Update So now that I understand what this line of code is doing, my question maybe unique in asking the following:

There is no negotiationApp object in the javascript code. window.negotiationApp will always be set to an empty object, it seems the developer is really just using this as a namespace or container for other objects. Is this a common javascript practice?

Thanks for the quick answers guys, it looks like the developer that wrote this code never creates a negotiationApp object and so basically its usage seems to be that of a namespace in his code. — Brian Ogden, Jun 09 '13 at 18:44
The same as `window.negotiationApp || (window.negotiationApp = {})` :) — Paul S., Jun 09 '13 at 18:45
More duplicates: http://stackoverflow.com/q/13268848/218196, http://stackoverflow.com/q/4087543/218196, http://stackoverflow.com/q/13016235/218196, http://stackoverflow.com/q/2802055/218196, http://stackoverflow.com/q/9604865/218196 -- Looks like we have to clean this up a bit. — Felix Kling, Jun 09 '13 at 18:46
@FelixKling, I updated my question as there may be one aspect of my question that makes this unique, if not I will be happy to delete the question if this is a stackoverflow best practice, but I don't want people that took the time to properly answer this question to lose their points... — Brian Ogden, Jun 09 '13 at 21:41
I'd just leave it be, Brian. No harm in a few more quality answers. — Michael Petrotta, Jun 10 '13 at 02:11

score 5 · Accepted Answer · answered Jun 09 '13 at 18:39

5

it makes sure that window.negotiationApp is set. If window does not have this property then it initializes it to be {} (an empty object), otherwise, it does nothing.

answered Jun 09 '13 at 18:39

akonsu

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Thanks for your answer, the developer that wrote this code does not ever create an negotiationApp object so it is always initialized as an empty object ({}), is this a common practice to achieve a namespace in javascript? – Brian Ogden Jun 09 '13 at 18:47
I do not know about how common this is, but most of the code that I have seen uses objects like this to put all the code's functionality in. – akonsu Jun 09 '13 at 18:50

score 2 · Answer 2 · answered Jun 09 '13 at 18:40

2

It's an idiom that basically means, if window.negotiationApp doesn't exist, set it to {}. You might do that so future info doesn't return undefined or something.

answered Jun 09 '13 at 18:40

Rich Bradshaw

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score 2 · Answer 3 · answered Jun 09 '13 at 18:40

Ensures window.negotiationApp object is not undefined.

window.negotiationApp = window.negotiationApp || {};

Means if window.negotiationApp is defined then use it or assign window.negotiationApp an empty object.

if(window.negotiationApp) {
  window.negotiationApp = window.negotiationApp;
}
else {
  window.negotiationApp = {};
}

score 2 · Answer 4 · answered Jun 09 '13 at 18:40

2

since this variable is set on the global scope, it makes sure not to override an existing one if there is any.

so it basically says, if there is already a negotiationApp variable defined - use it, if not create a new one.

answered Jun 09 '13 at 18:40

Tomer

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Can anyone tell me what this javascript might be doing

4 Answers4