trap-is-missing-target-is-proxy.js (864B)
1 // Copyright (C) 2020 Alexey Shvayka. All rights reserved. 2 // This code is governed by the BSD license found in the LICENSE file. 3 4 /*--- 5 esid: sec-proxy-object-internal-methods-and-internal-slots-preventextensions 6 description: > 7 If "preventExtensions" trap is null or undefined, [[PreventExtensions]] call 8 is properly forwarded to [[ProxyTarget]] (which is also a Proxy object). 9 info: | 10 [[PreventExtensions]] ( ) 11 12 [...] 13 4. Let target be O.[[ProxyTarget]]. 14 5. Let trap be ? GetMethod(handler, "preventExtensions"). 15 6. If trap is undefined, then 16 a. Return ? target.[[PreventExtensions]](). 17 features: [Proxy] 18 ---*/ 19 20 var target = new Proxy({}, { 21 preventExtensions: function(_target) { 22 return false; 23 }, 24 }); 25 26 var proxy = new Proxy(target, {}); 27 28 assert.throws(TypeError, function() { 29 Object.preventExtensions(proxy); 30 }); 31 32 reportCompare(0, 0);