The Tor Browser / file revision

 var global = 0;

 Object.defineProperty(Object.prototype, 0, {set: function() { global++; }});

 for (var x = 0; x < 20; ++x)

   [1,2];

 assertEq(global, 0);

 Object.defineProperty(Object.prototype, 1, {set: function() { global++; }});

 for (var x = 0; x < 20; ++x)

   [1,2];

 assertEq(global, 0);

 Object.defineProperty(Object.prototype, "b", {set: function() { global++; }});

 for (var x = 0; x < 20; ++x) {

   var s = { a:0, b:1, 0: 2, 1: 3 };

 }

 assertEq(global, 0);

 assertEq([42][0], 42);

 assertEq([42].length, 1);