What does 'this.x1 = options.x1 || 0'; mean in Javascript?

Question

Possible Duplicates:
What does "options = options || {}" mean in Javascript?
null coalescing operator for javascript?

Was reading some code and I saw this:

this.x1 = options.x1 || 0;

Never seen syntax like this before. What does it mean?

My assumption is its short hand for "if options.x1 exists, this.x1=options.x1, else this.x1=0". — Aakil Fernandes, Oct 19 '12 at 20:53
It should be mentioned that existing isn't the only criteria, the value should also evaluate to Boolean non-false. [See this jsFiddle](http://jsfiddle.net/JimmySawczuk/CRGa6/). — Jimmy Sawczuk, Oct 19 '12 at 20:56

canon · Accepted Answer · 2012-10-19T20:55:30.237

3

It's a coalesce... which means it'll assign 0 if options.x1 is falsy... and options.x1 otherwise.

edited Oct 19 '12 at 20:55

answered Oct 19 '12 at 20:54

canon

score 2 · Answer 2 · answered Oct 19 '12 at 20:54

2

Let this.x1 be the value of options.x1 if options.x1 has any truthy value. Otherwise let this.x1 be 0.

answered Oct 19 '12 at 20:54

jAndy

2 Answers2