Creating a global variable from a function's return value

Question

I'm looking at Addy Osmani's gist for a publication/subscription pattern here:

https://github.com/addyosmani/pubsubz/blob/master/pubsubz.js

He surfaces his object as a global like this:

;(function ( window, doc, undef ) {

var topics = {},
    subUid = -1,
    pubsubz ={};

....

getPubSubz = function(){
    return pubsubz;
};

window.pubsubz = getPubSubz();

What is the value of creating that getPubSubz function? Wouldn't it be more straightforward to simply write:

window.pubsubz = pubsubz;

He also uses undef although its not needed..

jantimon
– jantimon

2014-07-17 18:34:51 +00:00
Commented Jul 17, 2014 at 18:34 — jantimon
– jantimon, Commented Jul 17, 2014 at 18:34

StriplingWarrior · Accepted Answer · 2014-07-17 18:28:02Z

2

Yes, in this case, because getPubSubz is only called in one place, immediately after declaring it, it could safely be inlined.

It's hard to say exactly what the author had in mind, but in a growing code base there may be some value to having a "getter" function which could be modified if the act of getting the pubsubz object required more advanced logic.

answered Jul 17, 2014 at 18:28

StriplingWarrior

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2 Comments

Anonymoose Over a year ago

Could you give a concrete exmaple of how it will be useful? In other languages getters and setters are used for encapsulation but in this case I don't see the advantage.

StriplingWarrior Over a year ago

@Hazaart: If the code grows to access the pubsubz object from many different places, and then one day you realize that you want to use a different pubSubz instance depending on the state of a toggle variable, it would be nice to only need to change the implementation of the getPubSubz method, rather than everything that's accessing it. Of course, in that case, it would be unwise to expose the object as a global variable. As I said, it's hard to know what the author had in mind there.

username tbd · Accepted Answer · 2014-07-17 18:43:13Z

2

It absolutely would be.

There are only two potential reasons why a getter would be used in this case:

There was previously some additional code inside the getter (logging, perhaps)
Addy Osmani's just following good practice*, and including a getter—even adding the opportunity to add additonal code in the future.

Through the power of GitHub, we can actually eliminate option one, as the getter was added in its current state—so I think we can conclusively say that it's just a matter of good practice here.

^{*as jantimon alludes to in the comments below, this isn't particularly advantageous in most cases (including this one) and this code does not necessarily need to followed as an example.}

edited Jul 17, 2014 at 18:43

answered Jul 17, 2014 at 18:29

username tbd

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1 Comment

username tbd Over a year ago

@jantimon fine, it's not particularly advantageous for JS, you got me. Maybe just old habits from languages where it is good practice :)

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