gistfile1.js

Proxy.ForwardingHandler.prototype = {
    /***
    ** all traps use this.state.get[proxy] to retrieve the target
    */
    state: new WeakMap();
};

function ForwardingPair(target){// Could be Proxy.ForwardingPair too...
    var h = new Proxy.ForwardingHandler(); // Just a new object identity inheriting from all methods
    var p = Proxy.create(h);
    h.state.set(p) = target;
   
    return {handler: h, proxy: p};
}

// ... //


var target = {};
var {handler: h, proxy: p} = ForwardingPair(target); // destructuring is convenient here

// changing one trap
h.set = function(rec, name, value, proxy){
          var target = this.state.get(proxy); // reaching internal state from the new trap
          console.log("New set trap in forwarding proxy. Property name: "+name);
          target[name] = value;
        };

// ... //


p.ProxiesAreAwesome = 42;
// logs: "New set trap in forwarding proxy. Property name: ProxiesAreAwesome"
target.ProxiesAreAwesome; // 42. Forwarding went well too