Arbitrary object methods and properties in JavaScript

Question

I'm sure this has definitively been answered before, and I've tried to search for it.. maybe my search terms are wrong...

Basically I have an object myObject, and I have a set of defined properties and methods for it. What I want to do is be able to handle calls/references to properties and methods that I have not defined.

For example, let's say I have this:

var myObject = {
  someProperty : 'foobar',
  someFunction : function () { /* Do stuff */ }
}

Currently, if someone tries to make a call to myObject.someOtherFunction(), JavaScript yells and screams about it. What I want to do is setup a way to automatically handle that. So for example, instead of JavaScript throwing an error, my object just returns false. Is this possible?

Another way to look at it is this:

var myObject = {
  someFunction : function () { /* Do stuff */ }
  magicBucket : function () { /* Do stuff */ }
}

If I call myObject.someFunction(), well that is defined and does something. What I want to happen is if I were to for instance call myObject.someOtherFunction(), instead of JavaScript throwing an error, it would call myObject.magicBucket().

The reason is that I have a client that uses a third-party library on their site. They want to discontinue using it, but completely removing it is going to take a lot of time and effort. So as a short-term solution, they wanted to know if I could make a dummy file that basically does nothing. Well, this library uses several objects that has lots of methods. I could go through everything and make dummy objects, but I thought maybe there might be some easy "catch-all" method to do this.

Some have mentioned checking if the method exists first, wrapping it in a condition or try..catch, etc. Well, the point of this is that at this time I can't touch the actual calls to the methods. And since the overall goal is to eventually remove the coding altogether, it's not even applicable.

Answer 1

There's a special property called __noSuchMethod__ which does precisely what you just described. However it's a non-standard property. It only works in Firefox. Here's how you use it:

var o = {
    __noSuchMethod__: function (name, args) {
        alert(name); // prints the name of the method
        alert(args); // prints the array of arguments
    }
};

o.abc(1, 2, 3); // OUTPUT: abc 1,2,3

The future however are proxy objects. The following is a short tutorial on proxies: Proxy Tutorial