Self executing function as object property value in javascript

Question

Is it possible to have a self executing function which is an objects property value assign values to other properties in the object?

e.g. - what I would like to do is this:

var b={
  c:'hi',
  d:null,
  e:new function(){this.d=5}
};

But the "this" inside the new function seems to refer to b.e. Is it possible to access the b.e parent (i.e. b) from inside the function?

I can't see why you'd want to instantiate an anonymous function as you currently are. — Mitya
– Mitya, Commented Jul 27, 2012 at 12:44
What is your end goal here? To execute code during the object's creation that edits other properties of the object? — jackwanders
– jackwanders, Commented Jul 27, 2012 at 12:44
@jackwanders - yep. I was just wondering if it was possible to do it this way as a sort of shortcut to jakeclarckson's method below. — JJ_
– JJ_, Commented Jul 27, 2012 at 12:50
Work with functions! They are first-class objects in javascript, so they are very powerful. Never use the new operator! (Except for selfmade objects) Also you should read something about scope and closures in Javascript. — Christoph
– Christoph, Commented Jul 27, 2012 at 12:53
@Christoph I tried it using (function(){}()) but "this" inside the function referred to the Window object rather than b using the new operator seemed to be the only way to get access to b inside the function. — JJ_
– JJ_, Commented Jul 27, 2012 at 12:59

Christoph · Accepted Answer · 2012-07-27 13:03:16Z

7

This is how you do it.

Often called the module pattern (more info)

var b = function () {
   var c = 'hi';
   var d = null;

   return {
     c : c,
     d : d,
     e : function () {
       // this function can access the var d in the closure.
       d = 5;
     }
   }
}();

edited Jul 27, 2012 at 13:03

Christoph

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answered Jul 27, 2012 at 12:41

Hogan

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Comments

jabclab · Accepted Answer · 2012-07-27 12:42:32Z

1

You can access the value within the function, you just need to get rid of the new, i.e.

e: function () {
    this.d = 5;
}

answered Jul 27, 2012 at 12:42

jabclab

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2 Comments

JJ_ Over a year ago

Yeah but that wont assign the value to b.d unless I call b.e(). I was hoping to use a self executing function to do it.

Christoph Over a year ago

But then you have to explicitely call b.e() - this binds e to the the object b. Which is not the case with a selfexecuting function.

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