function Foo() { for (var i=0; i<10; i++) { this["p" + i] = i; } } function test1(foo) { for (var i=0; i<10400; i++) { foo.p1 = i; foo.p9 = i; var x = foo.p0 + foo.p1 + foo.p2 + foo.p8 + foo.p4 + foo.p5 + foo.p6 + foo.p7 + foo.p3 + foo.p9; assertEq(x, i + i + 35); } } test1(new Foo); function Bar(arg) { if (arg) { // Thwart definite-property analysis. this.x = 1; this.y = 2; this.z = 3; } } function test2(bar) { for (var i=0; i<10400; i++) { bar.x++; bar.y++; bar.z++; } assertEq(bar.x, 10401); assertEq(bar.y, 10402); assertEq(bar.z, 10403); } test2(new Bar(true));