michael@0: function f() {
michael@0:     var a;
michael@0:     for (var i=0; i<50; i++) {
michael@0:         a = [i, , [,, i*3], ];
michael@0:     }
michael@0:     return a;
michael@0: }
michael@0: Array.prototype[1] = 123;
michael@0: var arr = f();
michael@0: assertEq(arr.length, 3);
michael@0: assertEq(arr.toString(), "49,123,,123,147");