Define setter for hash member in JavaScript

Question

Hello. I have hash defined like this:

var props = {
    id: null,
    title: null,
    status: null
};

I'd like to define setter for status field (and only for it) doing it as following:

props.__defineSetter__("status", function(val){
    //Checking correctness of val...
    status = val;
});

But it doesn't work :( So, what's the right way to do it?

Answer 1

This should work:

props.__setStatus__ = function(val) {
    // Check correctness of val
    this.status = val;
}

Usage:

props.__setStatus__('Alive');

Answer 2

Simple, you need to use

this.status = val;

Otherwise you are just setting an unrelated global variable status equal to val.

And as already noted, setters/getters are not implemented in IE.

Also, I'm not sure about how wise it is to have a setter that is the same name as the property it sets. Not sure if this will result in a conflict, but it does seem like a bad idea yes? Ideally the variable that would be set should be hidden in a closure

var props = {
  id: null,
  title: null
};

(function() {

  var status;
  props.__defineSetter__("status", function(val){
    //Checking correctness of val...
    status = val;
  });

  props.__defineGetter__('status', function() { return status; });

}());

This way, status is fully protected from direct access, which is the point of using setters and getters.

Answer 3

The first thing is what MooGoo has pointed out. But also, you can not assign a property setter to an object using the same name as an existing variable in the object.

So your code would have to be something arround this:

var props = {
    id: null,
    title: null,
    hStatus: null,
};

props.__defineSetter__("status", function(v){
    this.hStatus = v;
});

props.__defineGetter__("status", function(){
    return this.hStatus;
});

[edit] Yeah, MooGoo eddited his answer faster then time time I took to write this 8(.