How to determine when a global variable is set in javascript?

Question

In javascript, I can determine when a global variable is set foo(assuming it was originally undefined) using Object.defineProperty:

var foo_;
Object.defineProperty(window, 'foo', {
  get: function() {
    return foo_;
  },
  set: function(newFoo) {
    console.log('foo set to ' + newFoo);
    foo_ = newFoo;
  }
});

Is there a more elegant way to do this? One drawback is that I cannot call Object.definePropertythe same property twice . Overriding an entire property just to determine when it is defined seems a bit overkill.

Can I use proxies somehow ? I feel like I need to make a proxy that targets the window object, though ... is this effective?

Answer 1

?

. , () _foo .

, Object.defineProperty . , , .

, configurable: true.

- ?

. . , , with (new Proxy(…)) { … }.

Answer 2

var _bar;
window.__defineGetter__("bar", function(){return this._bar});
window.__defineSetter__("bar", function(v){console.log("bar set to:",v); this._bar = v;});