The Tor Browser / file revision

 // defineProperty can set array elements

 var g = newGlobal();

 g.a = g.Array(0, 1, 2);

 var dbg = new Debugger;

 var gw = dbg.addDebuggee(g);

 var aw = gw.getOwnPropertyDescriptor("a").value;

 aw.defineProperty(0, {value: 'ok0'});  // by number

 assertEq(g.a[0], 'ok0');

 var desc = g.Object.getOwnPropertyDescriptor(g.a, "0");

 assertEq(desc.configurable, true);

 assertEq(desc.enumerable, true);

 assertEq(desc.writable, true);

 aw.defineProperty("1", {value: 'ok1'});  // by string

 assertEq(g.a[1], 'ok1');

 desc = g.Object.getOwnPropertyDescriptor(g.a, "1");

 assertEq(desc.configurable, true);

 assertEq(desc.enumerable, true);

 assertEq(desc.writable, true);