Associating data with an object without adding properties to it

[Justin Constantino]

I'm looking for the best way to have a function associate some bit of
data with an object so that it can recall it later, but without adding
any properties to the object - either because the data shouldn't be
seen or accessible by the user, or because the object is a host object
and doesn't necessarily allow properties to be added to it (from what I
understand). Basically, I want to do something like this:

function setData(obj, val) {
obj["someProp"] = val;
}
function getData(obj) {
return obj["someProp"];
}

without having to add -someProp- to -obj-. The only way I've come up
with is this:

var data = [];
function setData(obj, val) {
var n = 0;
while(n < data.length && data[n][0] != obj) n++;
data[n] = [obj, val];
}
function getData(obj) {
var n = 0;
while(n < data.length && data[n][0] != obj) n++;
return data[n] && data[n][1];
}

but since it requires that every item in the array be iterated over,
it's much slower than the original solution when it's used with a lot
of objects. Is there any better/more efficient way to do this?

[Baconbutty]

Re: Associating data with an object without adding properties to it

Using closures may give you a partial answer, at least for your own
objects.

It may be of no assistance for host objects, and it also involves
creating two methods.

function myObject()
{
var p={};

this.setPrivate =function(a,b)
{
p[a]=b;
}

this.getPrivate =function(a,b)
{
return p[a];
}
}

function fTest()
{
var oObj1=new myObject();
var oObj2=new myObject();

oObj1.setPrivat e("Test",2);
oObj2.setPrivat e("Test",3);

alert(oObj1.get Private("Test") );
alert(oObj2.get Private("Test") );
}

[Baconbutty]

Re: Associating data with an object without adding properties to it

Also, it may help if you could explain with an example the context.
I.e. for what purposes would you wish to associate specific data with a
specific object other than as a property.