javascript null conditional expression [duplicate]

Question

Possible Duplicate:
null coalescing operator for javascript?

In C#, you can do this:

var obj = newObject ?? defaultObject;

That says assign newObject to obj if not null else assign defaultObject. How do I write this in javascript?

There's an excellent answer to this question here: stackoverflow.com/a/476445/1010337 — ActiveDan
– ActiveDan, Commented May 28, 2012 at 4:41

Sampson · Accepted Answer · 2014-01-10 22:10:56Z

6

While it's considered an abusage, you can do the following:

var obj = newObject || defaultObject;

Note that if newObject is of any falsy value (such as 0 or an empty string), defaultObject will be returned as the value of obj. With this in mind, it may be preferred to use either the ternary operator or a standard if-statement.

var obj = ( "undefined" === typeof defaultObject ) ? defaultObject : newObject ;

edited Jan 10, 2014 at 22:10

answered May 28, 2012 at 4:33

Sampson

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3 Comments

user166390 Over a year ago

This is slightly different though, as it will result in defaultObject for any false-y value of newObject. That is, there is no "direct"-equivalent, so the ternary (??) with an explicit equality might capture a given intent better...

Sampson Over a year ago

@Lolcoder A boolean false is an actual false. Falsy values would be things like the number 0, or an empty string.

nnnnnn Over a year ago

@pst - While I agree with you, I would note that if you know in advance that defaultObject actually is an object then it will never be falsy.

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