Calling a function when passing no parameters

[Yansky]

If I have the following function:

function foo(){

alert('hi');

}

and I don't need to pass any parameters to it, is calling it this way:

foo;

the same as calling it this way:

foo();

 

[Joost Diepenmaat]

If I have the following function:

function foo(){

alert('hi');

}

and I don't need to pass any parameters to it, is calling it this way:

foo;

the same as calling it this way:

foo();

No. foo; does not call it at all. It's a statement returning the
function foo, but since you're not doing anything with the value it's
a useless statement.

A contrived example of foo; is:

var bar = foo; // assign function foo to bar
bar(); // call the function.

IOW, you do need the parentheses if you want to call a function.

 

[Yansky]

No. foo; does not call it at all. It's a statement returning the
function foo, but since you're not doing anything with the value it's
a useless statement.

A contrived example of foo; is:

var bar = foo; // assign function foo to bar
bar();  // call the function.

IOW, you do need the parentheses if you want to call a function.

Thanks for clearing that up.

 

[Yansky]

Thanks for clearing that up.

Oh wait I have one more question. What about when you're calling the
function inside an event listener? e.g.
function foo(){

alert('hi');

}
window.addEventListener("load", foo, false);

 

[Thomas 'PointedEars' Lahn]

That's probably the second most stupid question I have ever read on Usenet.

No. foo; does not call it at all. It's a statement returning the
function foo, but since you're not doing anything with the value it's
a useless statement.

A contrived example of foo; is:

var bar = foo; // assign function foo to bar
bar(); // call the function.

IOW, you do need the parentheses if you want to call a function.
[...]

Thanks for clearing that up.

I really wonder what is so difficult about trying something out before
asking (or to read the available reference material, including this
newsgroup's FAQ, for that matter). If you are this afraid that code that
you write could have effects this dangerous on the computer you are
developing on, you should forget all about programming and computer science,
and move to a happy little island nowhere near any technology.

<http://jibbering.com/faq/>
<http://catb.org/~esr/faqs/smart-questions.html>


PointedEars, shaking his head

 

[Thomas 'PointedEars' Lahn]

Oh wait I have one more question.

You don't say.

What about when you're calling the function inside an event listener?
e.g.
function foo(){

alert('hi');

}
window.addEventListener("load", foo, false);

`foo' refers to the (event) listener, which is the user-defined function.
Again, the function is _not_ called here, but being referred to. It is
called *later*, by the DOM implementation's event handler, using the passed
Function object reference.

RTFM. RTFFAQ. STFW.


PointedEars

 

[Yansky]

That's probably the second most stupid question I have ever read on Usenet.

w00t!

 

[Thomas 'PointedEars' Lahn]

w00t!

And that's definitely the most stupid reply I have ever read.

Congratulations. Don't you want to apply for the Darwin Award as well?


PointedEars

 

[Stevo]

Oh wait I have one more question. What about when you're calling the
function inside an event listener? e.g.
function foo(){
alert('hi');
}
window.addEventListener("load", foo, false);

That's fine, you're not calling it, you're nominating it as the function
that should be called.

Here, alias will be set to 3;

function foo(){return 3;};
var alias=foo();

Here, alias will become an actual alias of the function foo.

function foo(){return 3;}
var alias=foo;
//you can now do this:
alert(alias()); //alert 3