Create a Javascript Callback function?

Question

i was wondering how to implement a callback into this piece of code

MyClass.myMethod("sth.", myCallback);
function myCallback() { // do sth };

var MyClass = {

myMethod : function(params, callback) {

    // do some stuff

    FB.method: 'sth.',
       'perms': 'sth.'
       'display': 'iframe'
      },
      function(response) {

            if (response.perms != null) {
                // How to pass response to callback ?
            } else {
                // How to pass response to callback ?
            }
      });
}

}

jenming · Accepted Answer · 2011-02-24 22:42:06Z

13

three ways to achieve "// How to pass response to callback ?" :

callback(response, otherArg1, otherArg2);
callback.call(this, response, otherArg1, otherArg2);
callback.apply(this, [response, otherArg1, otherArg2]);

1 is the simplest, 2 is in case you want to control the 'this' variable's value inside your callbackfunction, and 3 is similar to 2, but you can pass a variable number of arguments to callback.

here is a decent reference: http://odetocode.com/Blogs/scott/archive/2007/07/05/function-apply-and-function-call-in-javascript.aspx

answered Feb 24, 2011 at 22:42

jenming

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1 Comment

Chris Baker Over a year ago

Very complete answer... nice!

Peter C · Accepted Answer · 2011-02-24 22:38:01Z

7

All you have to do is call the callback function the normal way. In this case you would just do callback(response).

var MyClass = {

myMethod : function(params, callback) {

// do some stuff

FB.method: { 'sth.',
   'perms': 'sth.'
   'display': 'iframe'
  },
  function(response) {

        if (response.perms != null) {
            // How to pass response to callback ?
            // Easy as:
            callback(response);
        } else {
            // How to pass response to callback ?
            // Again:
            callback(response);
        }
  });
}

}

answered Feb 24, 2011 at 22:38

Peter C

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Comments

Anurag · Accepted Answer · 2011-02-24 22:37:43Z

1

Just invoke the passed in function.

callback(response)

answered Feb 24, 2011 at 22:37

Anurag

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Comments

Chris Baker · Accepted Answer · 2011-02-24 22:38:35Z

1

You're close... just use the callback. In this instance, you can form a closure.

var MyClass = {

myMethod : function(params, callback) {

    // do some stuff

    FB.method: 'sth.',
       'perms': 'sth.'
       'display': 'iframe'
      },
      function(response) {

            if (response.perms != null) {
                callback(response);
            } else {
                // response is null, but you can pass it the same as you did above - if you want to.  Probably better to have a generic failure handler
                ajaxFailHandler();
            }
      });
}

answered Feb 24, 2011 at 22:38

Chris Baker

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Comments

Andreas Gohr · Accepted Answer · 2013-08-30 09:01:59Z

1

I think you can simply call callback(response.perms) there. You could also register it as a

member of your class:

  MyClass.cb = callback;

and later call it:

 MyClass.cb(response.perms)

edited Aug 30, 2013 at 9:01

user2730944

answered Feb 24, 2011 at 22:37

Andreas Gohr

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Comments

Makram Saleh · Accepted Answer · 2011-02-24 22:38:28Z

0

callback.call(null, response);

answered Feb 24, 2011 at 22:38

Makram Saleh

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Comments

fabian · Accepted Answer · 2011-02-24 22:40:42Z

0

MyClass.myMethod("sth.", myCallback);
var myCallback = function myCallback() { // do sth }

var MyClass = {

myMethod : function(params, callback) {

    // do some stuff

    FB.method: 'sth.',
       'perms': 'sth.'
       'display': 'iframe'
      },
      function(response) {

            if (response.perms != null) {
                callback();
            } else {
                callback();
            }
      });
}

}

answered Feb 24, 2011 at 22:40

fabian

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1 Comment

Chris Baker Over a year ago

Not sure why you posted this... but you're not passing the response variable to your callback. callback(response); will do the trick - as indicated in the other answers.

Jerod Venema · Accepted Answer · 2011-02-24 22:37:46Z

-1

You've got a reference to a function now. Just invoke it:

callback(response.perms);

answered Feb 24, 2011 at 22:37

Jerod Venema

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Comments

SergeS · Accepted Answer · 2011-02-24 22:34:35Z

-3

var callback = function() {

};

Thats it :-)

answered Feb 24, 2011 at 22:34

SergeS

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5 Comments

mellamokb Over a year ago

Wouldn't it be callback(response)?

Chris Baker Over a year ago

This does not seem to have any bearing on the question.

fabian Over a year ago

Well, I could just call callback() in the dephest method.

mellamokb Over a year ago

@fabian: Exactly, as the other 6 posters suggested :)

Chris Baker Over a year ago

fabian, I advise that you disregard this answer. This is not an answer to your question at all - this is completely unrelated.

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