michael@0: // for-of consults Array.prototype when it encounters a hole.
michael@0: 
michael@0: Array.prototype[1] = 'peek';
michael@0: var log = [];
michael@0: for (var x of [0, , 2, 3])
michael@0:     log.push(x);
michael@0: assertEq(log[1], 'peek');
michael@0: assertEq(log.join(), "0,peek,2,3");