Object Constructors and returns in Javascript

Question

function makeHttpRequest(url, success) {
 $.ajax({
        url: url,
   dataType: "jsonp",
crossDomain: true,
   mimeType: 'application/javascript', 
      async: false,
    success: success
  });
} 

   var actions = {
       get_min_hit_list_bounty: function (user_id) {
          makeHttpRequest("get_min_hit_list_bounty?target_id=" + user_id + "&", function (data) {
             var data = data['body'],
                xml = convert(data);
             this.min_cost = $(xml).find('min_cost').text();

         this.cost = function () {
            return this.min_cost;
         }
      });
   }
};
var myBounty = new actions.get_min_hit_list_bounty(user);
alert(myBounty.cost());

I cannot return anything from this type of object. I've read plenty on using prototype and using "this" to make it public, but I'm not getting any where. Could someone please explain why this does not work?

TypeError: Object [object Object] has no method 'cost'

You define function in makeHttpRequest() callback function, not in actions.get_min_hit_list_bounty object — zerkms
– zerkms, Commented Aug 12, 2012 at 22:04
There are many more functions in the actions than listed here. — Stormy Weather
– Stormy Weather, Commented Aug 12, 2012 at 22:25
well, I've explained why the code in your question doesn't work. What do you want to know now? — zerkms
– zerkms, Commented Aug 12, 2012 at 22:27

Hamish · Accepted Answer · 2012-08-12 22:32:22Z

1

This has nothing to do with object constructors.

Most importantly you're confusing how asynchronous calls work (the first A in AJAX!). The anonymous function in makeHttpRequest is called with the result of the request - which could be any time after the rest of the code executes, or not at all.

You'll need to make your code event driven - ie you make the AJAX request and run code when the response is returned.

for example:

var onSuccess = function(data) {
    var data = data['body'],
    xml = convert(data);
    // ... etc
}

makeHttpRequest(url, onSuccess);

answered Aug 12, 2012 at 22:32

Hamish

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3 Comments

Stormy Weather Over a year ago

Tried it this way but still no luck.

Stormy Weather Over a year ago

get_min_hit_list_bounty : function(user_id){makeHttpRequest("get_min_hit_list_bounty?target_id=" + user_id + "&", get_min_hit_list_bounty); var get_min_hit_list_bounty = function(data){ var data = data['body'],

Hamish Over a year ago

Well it looks like you're referencing get_min_hit_list_bounty before it's defined.

Artem Pianykh · Accepted Answer · 2012-08-12 23:31:19Z

0

I believe it should look like this:

var actions = {
       get_min_hit_list_bounty: function (user_id) {
            this.userId = user_id;
            this.min_cost = 999999;

            this.cost = function () {
                return this.min_cost;
            };

            this.getMinCost = function(callback) {
                var me = this;

                var queryString = [
                "get_min_hit_list_bounty?target_id=",
                this.userId,
                "&"].join("");

                makeHttpRequest(queryString, function (data) {
                    var data = data['body'],
                    xml = convert(data);
                    me.min_cost = $(xml).find('min_cost').text();
                    callback.apply(me);
                });
            }
        }
};

var myBounty = new actions.get_min_hit_list_bounty(user);

myBounty.getMinCost(function() {
    alert(this.cost());
});

You have to understand how asynchronous code works. It is not just a set of instructions that executes consequtively. Think of it in terms of events and callbacks. Google should help.

answered Aug 12, 2012 at 23:31

Artem Pianykh

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5 Comments

Stormy Weather Over a year ago

Changed the alert to alert(myBounty.min_cost); Now it works. Thanks :)

Artem Pianykh Over a year ago

@StormyWeather this.cost() or myBounty.cost() don't work properly?

Stormy Weather Over a year ago

no neither one of those. Uncaught TypeError: Object [object Object] has no method 'cost'

Artem Pianykh Over a year ago

@StormyWeather check your code. this.cost() works for me. Maybe you copied previous version of my code, where I forgot to add 'cost' function.

Stormy Weather Over a year ago

Yes you are correct. this.cost() works now. Thank you for your time and help as well. :)

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