Passing an object method by reference to another function in Javascript

Question

So I've been trying to get this callback working inside of an object and I was just wondering if:

1) it's possible, 2) special syntax is required.

So instead of just having a regularly declared function:

function callback() {}

And passing that to another function by reference:

doSomething(callback)

Im trying to pass an object property that contains a function:

   {
     prop: function() {}
   }

and send that as a call back.

The problem is, passing the reference of prop throws an error:

doSomething(prop):

throws: Uncaught SyntaxError: Unexpected token :

If a complete example is needed, let me know.

Thanks, Ken

** Edit **

Okay so after some confusion I'm typing a fairly complete example.

var obj = {
    init: function() {
        this.some_function(this.callback_function)
    },
    some_function: function(callback) {
      callback();
    },
    callback_function: function() {
      // Callback!
    }
}

This is throwing the unexpected token error unless I put the () when I pass this.callback_function as an argument to some_function().

Thanks and sorry for not posting a fuller-example earlier.

Ken

"This is throwing the unexpected token error": No, it doesn't. Just keep in mind that the this keyword does not refer to obj when obj.callback_function is called. — MaxArt
– MaxArt, Commented Aug 28, 2012 at 9:03

sbditto85 · Accepted Answer · 2013-08-05 14:37:19Z

3

I realize that this is not the solution to the OP's question but I google for "passing object methods as call backs" and this came up. I also found a link http://bitstructures.com/2007/11/javascript-method-callbacks.html which helped me understand how to do it in js. HTH

answered Aug 5, 2013 at 14:37

sbditto85

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1 Comment

Ken Over a year ago

Thanks for the response :) Though I solved this long ago, it's nice to know the community is a very helpful one.

MaxArt · Accepted Answer · 2012-08-27 16:12:57Z

1

Just pass the method:

var obj = {
    prop: function() {}
};
doSomething(obj.prop);

answered Aug 27, 2012 at 16:12

MaxArt

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3 Comments

Ken Over a year ago

Sorry, I'll post a full example in a bit - but this is what I am currently doing. Throws unexpected token error unless you include the () with the argument.

MaxArt Over a year ago

@Ken I'm still waiting for your example. I'm not sure I got you question, but I'm afraid that your actual problem is Javascript syntax.

Ken Over a year ago

sorry for taking so long, I'm on a family vacation and was shuttled out the door immediately after posting this.

Paul S. · Accepted Answer · 2012-08-28 02:53:58Z

1

When you do obj.func as an argument, it passes the function losing this from the scope.

some_function: function(callback) {
    callback.call(this);
},

answered Aug 28, 2012 at 2:53

Paul S.

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Comments

yngccc · Accepted Answer · 2012-08-27 16:28:13Z

0

you are mistyping the semicolon at the end of doSomething(prop):

answered Aug 27, 2012 at 16:28

yngccc

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1 Comment

Ken Over a year ago

Sorry - I typed that from my phone. Typing a full example now.

Ken · Accepted Answer · 2012-09-06 20:22:19Z

0

Sorry for the late response ( I was on vacation ), It was a syntax error, I forgot a comma delimiter in my object method.

answered Sep 6, 2012 at 20:22

Ken

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