JavaScript for Developers 36 - Functions as arguments

Thanks to functions being first class values, they can be passed as arguments to other functions. Let's see how that works!

[GrayCo]

Aha ! A big moment of understanding! Thanks for making some long-term confusion instantly get resolved.

[dnyaneshtathode]

Hey Koushik, wonderful explanation. Thanks for keeping it simple as usual.

[foreverandadave]

Thank you! I was watching another tutorial and he did this, but didn't explain it, and I was left scratching my head. After a bit of Googling, I found this video and it helped me immensely! Thank you very much!! Hoping to see some Vue stuff from you in the near future! :)

[anujkishor]

Hi, I just want to ask to ask about return statement, in the very first function if I provide a return statement then how can I access the return statement with the second function or pass a parameter for return statement.

[hehythrjkljwqoi]

There is no semicolon after the executor function.
It is defined to be as a value to a variable in the video.

Is it correct or JS interpreter just ignores it but it should be there?

[mudassarnazar]

hello there, can you show this with currying ?
I am struck in a middleware in redux project code where we are currying some action I am not getting an argument is being called as function/method.

export const loggerMiddleware = (store) => (next) => (action) => {
if (!action.type) {
return next(action);
}
console.log('type: ', action.type);
console.log('payload: ', action.payload);
console.log('currentState: ', store.getState());
next(action);//I am not getting this line
console.log('next state: ', store.getState());
};

[indraalapati]

Hi Koushik, i am not able to run javascript code from scratchpad. Should i download any plugins ? Please help me out. Thanks in advance.

[bitoutsid-ahmed]

hello, and thanks, just question, what if we have many argument like name, sruname and so on, and instead of console log return ?

[fredjohnson]

I understand callbacks in C++ where you pass a 'pointer to a function' to another thread and wait for the callback result. This does not appear to be the same as a C++ callback. Maybe I'm not understanding the usecase in javascript, but this seems pointless. What problem does this technique solve?

[sravanthihariprasad]

hi Kaushik, can you please explain me the output of this code


var f= function (){ console.log ("hello")};
var check = function(f)
{ console.log ("just checking " + f())};
check(f);
output is : hello
just checking undefined


Why there is undefined printed after "just checking"


thanks in anticitpation

[davidcoronado]

How does line 7 or fn know to call line 1 (var f)?

[vinaygandhi]

var f =function (name){
console.log("Hello "+name);
};

var executor = function(fn, name){
fn(name);
}
executor(f, "vinay");

From bottom line 3, why we have to give the argument name in that?

[Martin]

Why do functions get invoked as CALLBACK functions when stored in a variable? And yet when a normal function is stored in a variable it is not invoked. Where is the critical difference?

[athrims]

I was just trying some sample program to follow the tutorial and I came across the following behaviour.

var func = function(){
return 20;
};

function print(fn){
console.log(fn());
}

print(func);

When I use the function name as print, nothing gets printed to console, but print is not even a reserved word.
Can you please tell me why it behaves like this.

[wvvwwwvvw]

So what is the point of giving a _name_ in the function expression, if you cannot call it later on in the code?
Here is the example code with comments:

[anurangacse]

Would be great if you could have added the word "Call back" function concept in this.

[derenjeager]

hii! nice video! very informative!! can u please solve this doubt of mine.... in a function I have seen people put like function trial(obj){}. here, obj has some definite meaning or is like just some word.. pls reply asap

[burakyigit]

what is the advantage of this usage? Where can this be used fairly?

[LeeHongYee]

var f=function (){}; and function f(){}; seems to be the same thing.

[RameenFallschirmjager]

Over simplified. In real world scenarios it's much more complicated.