In Javascript, does it make sense to "declare" a variable that is a property of an object?

Question

I have a global object APP which I use as a namespace for variables and functions in my applicaton:

var window.APP = {};

Does it make sense to "declare" variables in this namespace before assigning them?

var APP.myvar = null;
APP.myvar = new Cls();

Or should I forget using var and just add properties when required to my APP object?

`var APP.myvar = null` isn't even valid syntax, so I'm not clear on what the question is here. — Chris Hayes, Aug 16 '14 at 20:16
Does it make sense to write code that will halt with a SyntaxError? No, no it doesn't. — cookie monster, Aug 16 '14 at 20:22

score 2 · Accepted Answer · answered Aug 16 '14 at 20:20

2

APP.myvar is property of APP object. There is no need to initialize it in a way post proposes as by default it's value is equal to 'undefined'.

BUT if you want to initialize APP.myvar with 'null' value, do it in this way

APP.myvar = null

answered Aug 16 '14 at 20:20

Egor Smirnov

603
4
17

score 1 · Answer 2 · answered Aug 16 '14 at 20:25

1

you don't need to declare a variable there. On the top of every JavaScript file just write

window.APP = window.APP || {}

that will declare it as an empty object if it is undefined, or leave it as window.APP if defined. Then you can just hang variables off of it as you please .

APP.yourVar = "something"

answered Aug 16 '14 at 20:25

Josh

119
2

I also think that you could shorten that first line to something like window.APP||= {} – Josh Aug 16 '14 at 20:26
You're thinking of the bitwise `|=` operator, which wouldn't make sense here. – cookie monster Aug 16 '14 at 20:27

In Javascript, does it make sense to "declare" a variable that is a property of an object?

2 Answers2