I want to use a anonymous function inside an object

Question

I have this code for a newsfeed that I want to use.

I want it to look kind of like this:

function News(){

    //Load new comments every 5 sec
    setTimeout((function(){
        console.log(this); //Returns Object #News
        this.loadNewsFeed();
    }).call(this),5000);

    this.loadNewsFeed = function(){
        // Implementation here
    }
}

The problem here is that it says the Object News doesn't have an method called loadNewsFeed!

I've already got it to work if I put the anonymous function outside the object News.

Like this:

var news = new News();
//Load new comments every 5 sec
(function loopNews(){
    news.loadNewsFeed();
    setTimeout(loopNews,5000);
})();

So how can I do this inside the object News?

[MDN](https://developer.mozilla.org/en-US/docs/DOM/window.setTimeout#The_.22this.22_problem) goes into some deatil about how to deal with the 'this' problem. — Andrew, Dec 10 '12 at 20:16
But you must be aware of the required browser support of `bind` https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Function/bind — David Rettenbacher, Dec 10 '12 at 20:18

David Rettenbacher · Accepted Answer · 2012-12-10T21:28:55.183

3

This should work:

function News()
{
    var self = this;

    this.loadNewsFeed = function(){
        // Implementation here
    };

    //Load new comments every 5 sec
    setInterval(function handler() // setInterval for endless calls
    {
        console.log(self); //Returns Object #News
        self.loadNewsFeed();
        return handler;
    }(), 5000);
}

Explanation:
call(this) invokes the handler directly - and returns undefined to setInterval which means that it's executed immediately but no handler is set.
The handler-function executes in global context so this is the window-object. The local variable self "injects" the current (and desired) this - as self.

Edit 2:
Now executes immediately and registers a handler.

edited Dec 10 '12 at 21:28

answered Dec 10 '12 at 20:13

David Rettenbacher

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This question was asked just yesterday - see here: http://stackoverflow.com/questions/13771889/setinterval-with-self-executing-function – David Rettenbacher Dec 10 '12 at 20:26
Hmm, after your update @Warappa it didn't work. Still says: #Object doesn't have an method called loadNewsFeed – Muqito Dec 10 '12 at 21:17
Oh, too many edits ;) - just move the handler-definition before setInterval then it works! – David Rettenbacher Dec 10 '12 at 21:28
Can you add a new answer?:o Because I don't really get it. :/ I want it to work like you wrote here: Now executes *immediately and registers* a handler. – Muqito Dec 10 '12 at 21:33
Hm... I just copied the code (and added `new News()`) and it works: http://jsfiddle.net/sfgVy/ – David Rettenbacher Dec 10 '12 at 21:42
I've learned my lesson. It was because I didn't declare the method BEFORE. I thought it didn't matter in this case so.. I thought of it as a regular "constructor" thing.. Sorry to bother. – Muqito Dec 10 '12 at 21:55

I want to use a anonymous function inside an object

1 Answers1