michael@0: // for-of on a slow Array consults the prototype chain when it encounters a hole.
michael@0: 
michael@0: var a = [0, , , 3];
michael@0: a.slow = true;
michael@0: Object.prototype[1] = 'peek1';
michael@0: Array.prototype[2] = 'peek2';
michael@0: 
michael@0: var log = [];
michael@0: for (var x of a)
michael@0:     log.push(x);
michael@0: assertEq(log[1], 'peek1');
michael@0: assertEq(log[2], 'peek2');
michael@0: assertEq(log.join(), "0,peek1,peek2,3");