Using function's return value in if statement

Question

Hopefully a quick question here.

Can you use a function's returned value in a if statement? I.e.

function queryThis(request) {

  return false;

}

if(queryThis('foo') != false) { doThat(); }

Very simple and obvious I'm sure, but I'm running into a number of problems with syntax errors and I can't identify the problem.

Perhaps you should post the problematic code with the syntax errors instead of this simple example that you could easily test for yourself. — user113716
– user113716, Commented Jul 15, 2011 at 13:48

Sai Kalyan Kumar Akshinthala · Accepted Answer · 2011-07-15 11:46:14Z

11

You can simply use

if(queryThis('foo')) { doThat(); }

function queryThis(parameter) {
    // some code
    return true;
}

edited Jul 15, 2011 at 11:46

Sai Kalyan Kumar Akshinthala

11.9k8 gold badges45 silver badges68 bronze badges

answered Jul 15, 2011 at 11:31

VMAtm

28.4k17 gold badges85 silver badges133 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Timo Over a year ago

Also interesting: why is return from if not possible as in Elixir

VMAtm Over a year ago

@Timo What do you mean by not possible? You can do if (some_check) { return 1; } else { return 0; }? Is it some kind of comment for advertise the other language?

Timo Over a year ago

It is not related to the question, the ternary op is what I was looking for: x = true?1:2

VMAtm Over a year ago

@Timo, oh, ok, sorry, didn't understand that first time.

Saeed Neamati · Accepted Answer · 2011-07-15 11:40:56Z

Not only you can use functions in if statements in JavaScript, but in almost all programming languages you can do that. This case is specially bold in JavaScript, as in it, functions are prime citizens. Functions are almost everything in JavaScript. Function is object, function is interface, function is return value of another function, function could be a parameter, function creates closures, etc. Therefore, this is 100% valid.

You can run this example in Firebug to see that it's working.

var validator = function (input) {
    return Boolean(input);
}

if (validator('')) {
    alert('true is returned from function'); 
}
if (validator('something')) {
    alert('true is returned from function'); 
}

Also as a hint, why using comparison operators in if block when we know that the expression is a Boolean expression?

Pete Duncanson · Accepted Answer · 2011-07-15 11:32:36Z

3

In sort, yes you can. If you know it is going to return a boolean you can even make it a bit simpler:

if ( isBar("foo") ) {
  doSomething();
}

answered Jul 15, 2011 at 11:32

Pete Duncanson

3,2563 gold badges27 silver badges35 bronze badges

Comments

Jonathan van de Veen · Accepted Answer · 2011-07-15 11:32:38Z

1

This should not be a problem. I don't see anything wrong with the syntax either. To make sure you could catch the return value in a variable and see if that solves your problem. That would also make it easier to inspect what came back from the function.

answered Jul 15, 2011 at 11:32

Jonathan van de Veen

1,02613 silver badges28 bronze badges

Comments

Barry Kaye · Accepted Answer · 2011-07-15 11:31:37Z

0

Yes you can provided it returns a boolean in your example.

answered Jul 15, 2011 at 11:31

Barry Kaye

7,7796 gold badges46 silver badges65 bronze badges

Collectives™ on Stack Overflow

Using function's return value in if statement

5 Answers 5

4 Comments

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

4 Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related