creating non existing method on an object in javascript

Question

How do getter or setter works on object in javascript ?

i.e.

In python if I call a nonexistent method on an object I could intercept the call via getter and setter and in turn return from getter and setter.

How do I do similar functionality in JavaScript ?

https://github.com/Flotype/now/blob/master/lib/client/now.js implements this functionality somehow. I didn't understand the trick. can anyone explain ?

@arxanas careful that's deprecated and only works in mozilla afaik — JaredMcAteer
– JaredMcAteer, Commented Aug 30, 2012 at 14:27
its non standard and deprecated, what about other methods ? ( or may be its not possible ? ) — iamgopal
– iamgopal, Commented Aug 30, 2012 at 14:27
I don't think there are other methods currently, the main workaround is to access everything by a main get and set method which then does the checking inside that method. — JaredMcAteer
– JaredMcAteer, Commented Aug 30, 2012 at 14:29

Exelian · Accepted Answer · 2012-08-30 14:46:30Z

1

Creating the same functionality is virtually impossible in Javascript. My best guess would be something like this:

var getter = function (propName) { 
    if (propName in this) { 
        return this[propName]; 
    } else { 
        return "no prop"; 
    } 
};

You can call this function on any object you like using this syntax:

a = { "test": "yes" };
b = {}
console.log(getter.call(a, "test"));
console.log(getter.call(b, "test"));

It's not the best solution but I don't think there's a better way.

answered Aug 30, 2012 at 14:46

Exelian

5,9381 gold badge33 silver badges51 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Quadroid · Accepted Answer · 2012-08-30 15:39:39Z

1

1) You can use non-standart mozilla __noSuchMethod__ property.

2) EcmaScript 6 Harmony propose the Proxy object. See Simulating __noSuchMethod__

answered Aug 30, 2012 at 15:39

Quadroid

8252 gold badges9 silver badges15 bronze badges