Question

I am new here so I hope I do not violate any rules…

It is so that I am working on object inheritance in JavaScript… and are figuring out “my” rules for this thing… And now I have come to “some” sort of a problem…

this is what I like to do:

I like to have an method (function) that is more an identifier for the object I am creating, this method is also the objects creator… However I also wish to use that same object to instantiate the “datatype” the object created (I guess code explains more so… here is the piece I am stuck with)

    TRecord = function() {
      this.Class = 'TRecord';
      F = function() {};
      F.prototype = arguments[0]; //args is an object (se below)
      return(new F());
    };

    TRecord.create = function(O) { // this method will not be executed as I like
        if(O) alert(O.Class);      // inside above object when define there with
        <new O object created and returned - code missing>
    };                             // this.create = function(){};
                                   // but if defined here it will, se below...

    TMessage = TRecord({
      'Class': 'TMessage',
      'msgID': Number(0),
      'data': Object('Hello')
    });

    aMSG = TRecord.create(TMessage); // the TMessage instance will be created
                                     // with the above method... and
    alert(aMSG.Class);               // will output TMessage...

why can’t I implement the TRecord.create function inside TRecord ?

…
I have some trouble posting the whole source.js (the formatting do not work) so this will have to due, I do however have some other constructors/creator functions for “real” function (class) objects and not records (data objects)… that works – these are Implemented a bit different though, with support for deep inheritance…

Answer 1

The this keyword refers to the scope under which a function is called. In your example:

TMessage = TRecord({...});

TRecord will be called with the global or window object as its scope, or in strict mode, undefined. The this keyword only refers to a new object inside of a constructor function because of how the new keyword boxes a call with the new scope.

For more information, please see https://developer.mozilla.org/en/JavaScript/Reference/Operators/this