Returning a function from a function without calling the returned function

Question

Can it be done?

I have the following:

populate.func = function(node, state) {
    return (new function(data) { /* stuff*/ });
}

However, calling populate.func invariably calls both the called function and the returned function, whether I use regular calling convention or the call method. I want to be able to call populate.func and just return the function as a value to make use of, without actually running it...

why new? it should work without it. i mean, say infunc = function(data){ /* stuff*/ }; You do: return infunc; — Prasanth
– Prasanth, Commented Aug 7, 2012 at 6:03
New because I read that this was a trick to pass a function by reference and pass variable in the state it was in when you passed the function as an argument, and not when it gets called. I think it does this because so long as a pointer is maintained to the child function, the parent can't be garbage collected either, nor its call stack. Or something. — Rob F
– Rob F, Commented Aug 7, 2012 at 6:09
@RobF you have been terribly misinformed, go read up some more on javascript... — Willem D'Haeseleer
– Willem D'Haeseleer, Commented Aug 7, 2012 at 6:10

Willem D'Haeseleer · Accepted Answer · 2012-08-07 06:03:08Z

1

just do this

populate.func = function(node, state) {
    return (function(data) { /* stuff*/ });
}

Your code is instantiating a new object using your function as a constructor function, but you want to return a reference to your function instead, so just drop the new keyword.

answered Aug 7, 2012 at 6:03

Willem D'Haeseleer

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6 Comments

Rob F Over a year ago

That seems to have worked. Will wait and experiment a bit before leaving feedback. Why did new operator cause it to call both functions?

Willem D'Haeseleer Over a year ago

because you executed the function to instantiate an object from it, using the function as a constructor function.

Rob F Over a year ago

That doesn't answer the question.

Vatev Over a year ago

@RobF It does, that is exactly the reason why it calls the function. You should read up on what new does in JS.

Willem D'Haeseleer Over a year ago

@RobF do you feel like you understand what i tried to say or is it still unclear ?

|

Vatev · Accepted Answer · 2012-08-07 06:03:00Z

0

I'm not even sure what your code is actually doing, but I think what you want is:

populate.func = function(node, state) {
    return function(data) { /* stuff*/ };
}

answered Aug 7, 2012 at 6:03

Vatev

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2 Comments

Willem D'Haeseleer Over a year ago

@RobF adding in new doesn't make any diffrence there, you are returning an object by reference, instantiated by your constructor function, but not the function it self.

Vatev Over a year ago

return function... will return a reference to the function w/o executing it.

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