How to access this variable in Object.defineProperty value flag?

Question

I'm attempting to find a way to initialize a property value that is appended to all instances of a JavaScript pseudoclass with localized value references without the need to manually iterate over every instance, as an example the following code:

function A() {
    this.a = '0';
}

var a = new A();
var b = new A();

document.write(a.a + a.b + a.c + '<BR />');

A.prototype.b = '1';
Object.defineProperty(A.prototype, 'c', {
    writable: true,
    value: (function() { return(this.a + '|'); })()
});

document.write(a.a + a.b + a.c + '<BR />');

b.c = '3';

document.write(a.a + a.b + a.c + '<BR />');
document.write(b.a + b.b + b.c + '<BR />');

Outputs:

0undefinedundefined
01undefined|
01undefined|
013

But under the desired condition would output:

0undefinedundefined
010|
010|
013

Edit:

For clarification, the value should be initialized to the properties of the object accessed via "this." when the property is appended to the object, not in a delayed manner on a get or set call and without using additional local properties.

Answer 1

You seem to want a getter function that dynamically computes the value from the a property:

Object.defineProperty(A.prototype, 'c', {
    get: function() {
        return(this.a + '|');
    },
    set: function(x) { // overwritable:
        // create normal property directly on the object (not on the prototype)
        Object.defineProperty(this, 'c', {
            value: x,
            writable: true
        });
    }
});

Your current code works like

A.prototype.c = (function() { return(this.a + '|'); })(); // IEFE

where this is the global object and a of course undefined.