JS ES6 IIFE + Symbol & Prototype - Adding to Instance?

Question

I realize my question's title may be worded weirdly, so I apologize up front. To be clear, I am referring to this:

var IIFE = (function () {
    var a = Symbol("a");
    function IIFE() {
        this["a"] = null;
    }
    IIFE.prototype = {
        get a() { return this[a]; },
        set a(n) { this[a] = n; }
    }
    return IIFE;
}());
var iife = new IIFE;

I want to dynamically add 'b' & 'c' using an array:

var arrProps = ['b','c'];

to an instance of IIFE. I don't care how it gets done, so as long as the values specified within arrProps can be accessed & assigned the same as you would with 'a' inside the instance, outside the instance, and within prototype get/set. An example of using 'b' would be:

• inside the instance: this["b"] = value;
• outside of the instance: iife.b = value;
• prototype set/get: this[b] = value;

As far as the get/set internals go, there is nothing more than just getting the value and setting value.

Any help would be very much appreciated.

Answer 1

Instead of using a Symbol, have the function return a Proxy instead, and you can use its get and set traps to check for accesses/assignments to arbitrary properties:

 const proxy = new Proxy({}, { get(obj, prop) { console.log('getting'); return obj[prop]; }, set(obj, prop, newVal) { console.log('setting'); return obj[prop] = newVal; }, }); proxy.a = 'aVal'; console.log(proxy.a); proxy.b= 'bVal'; proxy.c = 'cVal'; proxy.a = 'anotherAVal';