Can I omit the else in an inline javascript if statement?

25
votes

I'm trying to use this and it doesn't appear to be working. I'm guessing it's just not an option, but want to confirm. Is this valid?

(if_it_is) ? thats_cool();
7
javascript
No, it's not optional. Use a binary operator instead (&&) as long as thats_cool() returns a value that evaluates to true. - Jonathan M
Nope. It needs to have the : and some value following it. If you want, you could just create a function named do_nothing() that...well, does nothing. - Edwin
user1048967, That is called if() {}. - Dykam
@Jonathan It doesn't have to return boolean, as it'll be called if if_it_is evaluates to a truthy statement. - Edwin
@Edwin, that's a good catch. Thanks. - Jonathan M

7 Answers

50
votes

You can use && there:

if_it_is && thats_cool();

It is basically equal to:

if (your_expression){
   thats_cool();
}
5
votes

What you are trying to use is a Ternary Operator. You are missing the else part of it.

You could do something like:

(if_it_is) ? thats_cool() : function(){};

or

(if_it_is) ? thats_cool() : null;

Or, as others have suggested, you can avoid the ternary if you don't care about the else.

if_it_is && thats_cool();

In JavaScript, as well as most languages, these logical checks step from left to right. So it will first see if if_it_is is a 'trusy' value (true, 1, a string other than '', et cetera). If that doesn't pass then it doesn't do the rest of the statement. If it does pass then it will execute thats_cool as the next check in the logic.

Think of it as the part inside of an if statement. Without the if. So it's kind of a shorthand of

if (if_it_is && thats_cool()) { }
4
votes

No, it's not valid.

The conditional operator takes the form x ? y : z. The third operand is not like the else in an if, it always has to be there.

2
votes

You can't accomplish that using the ternary operator, but you can use the short-circuit nature of && to do what you want.

(if_it_is) && thats_cool();
1
votes

No, you can't. ?: is a ternary operator and MUST have all three of its operands.

1
votes

No, you can't. It's not an "inline if statement", it's the ternary operator, and that is, well… ternary.

(if_it_is) ? thats_cool() : null;

Since you do not seem to be interested in the return value of the operation, you could just write:

if (if_it_is) thats_cool();

though. That would also be better style than using a ternary.

0
votes

You miss the third component. Should be something like that:

(if_it_is) ? thats_cool() : not_too_cool();

The whole sense is:

condition ? do_something_if_condition_is_true : do_something_if_condition_is_false;