Question

I want to be able to assign a property to a function inside the function itself. I do not want to assign it to the object of invocation. So I want the equivalent of doing this:

var test  = function() {                    
    return true;         
};

test.a = 'property on a function';
alert(test.a);

Instead of this, where the property is assigned to a global object:

var testAgain = function() {
   this.a = "this property won't be assigned to the function";

   return true;  
};

testAgain();
alert(window.a);

Edit: To clarify, I’m wondering if there’s something like this:

var test = function() {
   function.a = 'property on a function';
};
alert(test.a); // returns 'property on a function'

Without knowing that the function is called test or having to execute it.
I know of course this isn’t valid syntax

Answer 1

[is there a way to set a property on a function] without knowing that the function is called test or having to execute it.

Emphasis mine.

You can set a property on a function without knowing what its global variable name is necessarily going to be, however you do have to have a reference to the function in one way or another.

The module pattern is as close of a fit as I can think of:

window.test = (function () {
    //the function could be named anything...
    function testFn() {
        ...code here...
    }
    //...so long as the same name is used here
    testFn.foo = 'bar';
    return testFn;
}());
window.test.foo; //'bar'

The outer closure prevents testFn from being accessed anywhere globally, so all other references will have to use window.test.

---

_{This part of the answer is associated with the prior version of the question.}

The simplest way of doing this is to use a named function:

var test = function testFn() {
    testFn.foo = 'bar';
    return true;
};

test.foo; //undefined
test();
test.foo; //'bar'

A better way of doing this is to use the module pattern so that you don’t accidentally create issues with global leakage:

var test = (function () {
    function ret() {
        ret.foo = 'bar';
        return true;
    }
    return ret;
}());

test.foo; //undefined
test();
test.foo; //'bar'