What means "|| {}" in Javascript?

Question

As in here for example:

var h , aa = aa || {} , m = this ,

What's the meaning of "|| {}" ?

`aa = itself OR empty_object` – adeneo Apr 25 '16 at 14:24 — adeneo, Apr 25 '16 at 14:24

score 5 · Answer 1 · 2016-04-25T14:36:32.387

5

It prevents you object from being undefined. E.g. if you write:

a = B || {};

and B will be undefined --> you will assign empty object instead of FALSY value (undefined).

Sum up: if value is "falsy value" assign empty object.

Here you have all falsy values:

edited Apr 25 '16 at 14:36

answered Apr 25 '16 at 14:24

2

This gets my +1 because it mentions the value can be any "falsy" value – Matti Virkkunen Apr 25 '16 at 14:25

score 0 · Answer 2 · answered Apr 25 '16 at 14:24

0

aa = aa || {}

This is setting a default value for the variable aa. If aa isn't "truthy" at the time this line executes, it will set it to {}.

answered Apr 25 '16 at 14:24

amphetamachine

score 0 · Answer 3 · answered Apr 25 '16 at 14:25

0

It's a default initialization in case aa is falsy. If aa is falsy (undefined, 0, empty string,...), aa is initialized to an empty object.

answered Apr 25 '16 at 14:25

fikkatra

3 Answers3