callback in nested function

Question

i have a function which calls the another function and so on.

function A(args,callback){    
// make ajax request
//  on response 
    B()    
}

function B(args){

// make ajax request
//  on response 
    C()
}

function C(args){

  // make ajax request
  //  on response 
    D()
}

I am making such ten ajax calls. Two questions...

can anyone explain me what is callback-hell? Is this a callback Hell?
If i call callback() inside function D, will it get called. I am not passing callback as argument to my other functions.

I would think really hard before doing 10 ajax calls in a row that all depended on each other, if that's what you're saying. — Evan Trimboli
– Evan Trimboli, Commented Nov 14, 2012 at 20:31
I'm not familiar with a well-established definition for "callback hell", but I would call many deeply-nested callbacks "callback spaghetti". — apsillers
– apsillers, Commented Nov 14, 2012 at 20:33
@apsillers. LOL, my thoughts exactly, BTW I've found the definition to that phrase, look below. — gdoron
– gdoron, Commented Nov 14, 2012 at 20:34

gdoron · Accepted Answer · 2012-11-14 22:01:36Z

3

I don't know what you're calling callback hell but it's one hell of a spaghetti code.

What is "callback hell"?
Asynchronous javascript, or javascript that uses callbacks, is hard to get right intuitively.

Source

2.No, callback is not defined inside D so you will get an Error.

edited Nov 14, 2012 at 22:01

answered Nov 14, 2012 at 20:32

gdoron

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2 Comments

theJava Over a year ago

Lets take if i pass my callback reference from A to B and C then receive it in D... will i able to achieve.

gdoron Over a year ago

@theJava, Yes, in that case it will be valid, probably spaghetti but valid. I've never seen a good reason for doing 10 async operations one after the other. usually when those kind of things are being done, it's a mistake.

Konstantin Dinev · Accepted Answer · 2012-11-14 20:32:14Z

1

Inside D() there is no way to call callback because it is not defined there. What I mean by this is as long as you don't pass arguments down the callbacks then you are not having your callback variable inside D(). Callback hell is a situation where callbacks call each-other meaning A() calls B() and B() calls A().

answered Nov 14, 2012 at 20:32

Konstantin Dinev

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4 Comments

Bergi Over a year ago

Imho you don't need (endless) "recursion" for a callback hell.

Konstantin Dinev Over a year ago

@Bergi You are right, but callbacks are not that hard to debug, but the real hell is when callbacks are constantly calling each-other, because then debugging results in a different output than what you would get if you do not breakpoint inside the callbacks :)

theJava Over a year ago

If i pass my callback reference via A to B and B to C an then C to D... will that result in callback hell

Konstantin Dinev Over a year ago

@theJava This begs to the question is dynamic programming a callback hell? In your case I would not call it a callback hell.

Anoop · Accepted Answer · 2012-11-14 20:32:59Z

0

We can pass function reference as a parameter in JavaScript and use this reference to call related function whenever/ wherever we want.

for more info see this link http://recurial.com/programming/understanding-callback-functions-in-javascript/

answered Nov 14, 2012 at 20:32

Anoop

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