| // Copyright (C) 2020 Alexey Shvayka. All rights reserved. |
| // This code is governed by the BSD license found in the LICENSE file. |
| |
| /*--- |
| esid: sec-proxy-object-internal-methods-and-internal-slots-isextensible |
| description: > |
| If "isExtensible" trap is null or undefined, [[IsExtensible]] call is |
| properly forwarded to [[ProxyTarget]] (which is also a Proxy object). |
| info: | |
| [[IsExtensible]] ( ) |
| |
| [...] |
| 4. Let target be O.[[ProxyTarget]]. |
| 5. Let trap be ? GetMethod(handler, "isExtensible"). |
| 6. If trap is undefined, then |
| a. Return ? IsExtensible(target). |
| |
| IsExtensible ( O ) |
| |
| 1. Assert: Type(O) is Object. |
| 2. Return ? O.[[IsExtensible]](). |
| |
| [[IsExtensible]] ( ) |
| |
| [...] |
| 7. Let booleanTrapResult be ! ToBoolean(? Call(trap, handler, « target »)). |
| [...] |
| 10. Return booleanTrapResult. |
| features: [Proxy] |
| ---*/ |
| |
| var array = []; |
| var arrayExtensible = true; |
| var arrayTarget = new Proxy(array, { |
| isExtensible: function() { |
| return arrayExtensible; |
| }, |
| }); |
| |
| var arrayProxy = new Proxy(arrayTarget, { |
| isExtensible: undefined, |
| }); |
| |
| assert(Object.isExtensible(arrayProxy)); |
| |
| Object.preventExtensions(array); |
| arrayExtensible = false; |
| |
| assert(!Object.isExtensible(arrayProxy)); |