get a callback function to add to object javascript

Question

I have an issue with a method ive created for an object ive created. one of the methods requires a callback to another method. the problem is i cant add the data to the object that called the method. it keeps coming back as undefined. otherwise when i send the data to the console it is correct. how can i get the data back to the method?

var blogObject = new Object();
var following = [...];

//get posts from those blogs

blogObject.getPosts = function () {
    var followersBlogArray = new Array();

    for (var i = 0; i < this.following.length;i++){
        var followersBlog = new Object();

   // get construct blog url

        var complete_blog_url = ...;

i call the getAvatar function here sending the current user on the following array with it.

   followersBlog.avatar = blogObject.getAvatar(this.following[i]);

that part goes smoothly

   followersBlogArray.push(followersBlog);
   }
   this.followersBlogArray = followersBlogArray;
 }

here is the function that gets called with the current user in following array this function calls an ajax function

blogObject.getAvatar = function (data) {
console.log("get avatar");
     var url = "..."

this ajax function does its work and has a callback function of showAvatar

          $(function() {
                         $.ajax({
                                type: "GET",
                                dataType: "jsonp",
                                cache: false,
                                url: url,
                                data: {
                                    jsonp:"blogObject.showAvatar"
                                }
                          });

});

}

this function gets called no problem when getAvatar is called. i cant however get it to add the data to the followersBlog object.

blogObject.showAvatar = function (avatar) {

    return avatar

}

everything in here works fine but i cant get the showAvatar function to add to my followersBlog object. ive tried

blogObject.showAvatar = function (avatar) {
this.followersBlog.avatar = avatar; 
    return avatar

}

that didnt work of course. it shows up as undefined. can anyone help?

so somethings like...

$(function() {
                         $.ajax({
                                type: "GET",
                                dataType: "jsonp",
                                cache: false,
                                url: url,
                                complete: function () {
 this.avatar = data;
 }

                                                            data: {
                                    jsonp:"blogObject.showAvatar"
                                }
                          });

});

}

'complete: function () { blah; }'

cohs
– cohs

2012-09-06 02:30:05 +00:00
Commented Sep 6, 2012 at 2:30 — cohs
– cohs, Commented Sep 6, 2012 at 2:30

Russ · Accepted Answer · 2012-09-06 02:14:20Z

1

Welcome to the world of asynchronous programming.

You need to account for the fact that $.ajax() will not return a value immediately, and Javascript engines will not wait for it to complete before moving on to the next line of code.

To fix this, you'll need to refactor your code and provide a callback for your AJAX call, which will call the code that you want to execute upon receiving a response from $.ajax(). This callback should be passed in as the complete argument for $.ajax().

answered Sep 6, 2012 at 2:14

Russ

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Comments

Joel Purra · Accepted Answer · 2012-09-06 03:07:40Z

0

The correct option for setting the JSONP callback is jsonpCallback. The recommendation from the API for .ajax(...) is to set it as a function.

{
  // ...
  jsonpCallback: function (returnedData) {
    blogObject.showAvatar(returnedData);
  },
  // ...
}

answered Sep 6, 2012 at 3:07

Joel Purra

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