Javascript dynamic objects

Question

I don't really know the correct words to describe what I am trying to do, but the functionality is very similar to overriding the __get() function of PHP classes. For example this is what I want to do.

var obj = {
    param1:'a',

    func1:function(){ return '1';},

    catch_all:function(input){
        return input;
    }
}

//alerts 'a'
alert( obj.param1 );

//alerts '1'
alert( obj.func1() );

//alerts 'anything'
alert( obj.anything );

Basically I want a way to redirect any unused key to a predefined key. I have done some research on this and really didn't know what to search for. Any help is greatly appreciated. Thanks.

See also: http://stackoverflow.com/questions/2266789/is-there-an-equivalent-of-the-nosuchmethod-feature-for-properties-or-a-way/3757676#3757676 — Christian C. Salvadó, Dec 08 '11 at 22:10

score 2 · Answer 1 · answered Dec 08 '11 at 20:56

You can make a get function, but aside from that you cannot do what you intend.

A get function:

var obj = {
    param1:'a',

    func1:function(){ return '1';},

    get: function(input){
        return this[input] !== undefined ? this[input] : 'ERROR';
    }
}

//alerts 'a'
alert( obj.param1 );

//alerts '1'
alert( obj.func1() );

//alerts 'ERROR'
alert( obj.get('anything') );

Fiddle: http://jsfiddle.net/maniator/T2gWx/

score 2 · Accepted Answer · answered Dec 08 '11 at 20:58

2

This is impossible with the current JavaScript implementations. There is not any kind of default getter as you have in ObjC or other languages.

answered Dec 08 '11 at 20:58

Adilson de Almeida Jr

2,761
21
37

Dhwanit · Answer 3 · 2013-08-10T19:11:45.587

1

Kindly find the changes in the code of get method. It is able to modify the memory value reference by obj's param1.

var obj = {
    param1:'a',

    func1:function(){ return '1';},

    get: function(input){
        this.param1 = input;
        return input;
    }
}

//alerts 'a'
alert( obj.param1 );

//alerts '1'
alert( obj.func1() );


//alerts 'anything'
alert( obj.param1 );

edited Aug 10 '13 at 19:11

answered Aug 10 '13 at 14:22

Dhwanit

610
1
9
17

score 0 · Answer 4 · answered Dec 08 '11 at 21:04

0

I think what you want are called harmony proxies.

http://wiki.ecmascript.org/doku.php?id=harmony:proxies&s=proxy

They aren't in JavaScript yet, at least not in any current web browser implementations.

answered Dec 08 '11 at 21:04

Jamund Ferguson

16,721
3
42
50

Javascript dynamic objects

4 Answers4