1 2 3 4 5 6 7 8 9
var x = [1, 2, , 4] x[100000] = 1; var y = Object.create(x); y.a = 1; y.b = 1; var arr = []; for (var z in y) arr.push(z); assertEq(arr.join(), "a,b,0,1,3,100000");