The Tor Browser / file revision

 // Array iterators reflect changes to elements of the underlying array.

 load(libdir + "asserts.js");

 load(libdir + "iteration.js");

 var arr = [0, 1, 2];

 var it = arr[std_iterator]();

 arr[0] = 1000;

 arr[2] = 2000;

 assertIteratorNext(it, 1000);

 assertIteratorNext(it, 1);

 assertIteratorNext(it, 2000);

 assertIteratorDone(it, undefined);

 // test that .keys() and .entries() have the same behaviour

 arr = [0, 1, 2];

 var ki = arr.keys();

 var ei = arr.entries();

 arr[0] = 1000;

 arr[2] = 2000;

 assertIteratorNext(ki, 0);

 assertIteratorNext(ei, [0, 1000]);

 assertIteratorNext(ki, 1);

 assertIteratorNext(ei, [1, 1]);

 assertIteratorNext(ki, 2);

 assertIteratorNext(ei, [2, 2000]);

 assertIteratorDone(ki, undefined);

 assertIteratorDone(ei, undefined);