var theO; function deleteAll() { delete theO.a; delete theO.b; delete theO.c; delete theO.d; for (var i = 0; i < 10; ++i) theO["i" + i] = 42; theO.a = 11; theO.b = 12; theO.c = 13; theO.d = 14; } function foo(o_) { var o = o_; var result = 0; for (var s in o) { result += o[s]; deleteAll(); } return result; } noInline(foo); for (var i = 0; i < 10000; ++i) { var result = foo(createProxy(theO = {a:1, b:2, c:3, d:4})); if (result != 1 + 12 + 13 + 14) throw "Error: bad result: " + result; }