let invoked = false; Object.defineProperty(Array.prototype, '0', {set: function () { invoked = true; }}); let result = [1, 2, 3].slice(1); assertEq(invoked, false); let proxy = new Proxy({}, { get: function (target, name, proxy) { switch (name) { case "length": return 2; case "0": return 15; case "1": // Should not invoke [[Get]] for this hole. default: assertEq(false, true); } }, has: function (target, name) { switch (name) { case "0": return true; case "1": return false; default: assertEq(false, true); } } }) result = Array.prototype.slice.call(proxy, 0); assertEq(result.length, 2); assertEq(0 in result, true); assertEq(1 in result, false); assertEq(result[0], 15);