Explicitly Returning a value from a constructor in javascript

Question

http://ejohn.org/blog/building-a-javascript-library/

In the above link John Resig Suggests calling and returning new foo in a constructor if the caller originally forgot to.

that makes some sense to me, but then I get a strict error because my constructor does not 'always' return a value. Upon gaining a little understanding of constructors in javascript, i stopped returning this because new automatically does that.

My question is, should I ...

Not use the defensive technique described?
return this at the end of my constructor?
Mystery option that I am ignorant of?

tobyodavies · Accepted Answer · 2011-01-27 03:45:15Z

4

returning this is pointless because if the caller forgot to add new then this will be the document, not an instance of foo. What i usually do is start a constructor with if(! (this instanceof foo)) return new foo(); or something to that effect

Edit: after a more careful read, if you want to avoid strict errors and you are doing this already, yes, return this at the end is usually a good idea

edited Jan 27, 2011 at 3:45

answered Jan 27, 2011 at 2:57

tobyodavies

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2 Comments

griotspeak Over a year ago

right, that is the suggestion that led me to the question. If I explicitly return during an error, I get a strict warning because i implicitly return when all goes well

tobyodavies Over a year ago

yep, so returning this if all goes well is probably a good idea

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