Strict mode Passingnon-Strict mode Passing
Features:
- Proxy
- Symbol.isConcatSpreadable
// Copyright (C) 2016 the V8 project authors. All rights reserved. // This code is governed by the BSD license found in the LICENSE file. /*--- esid: sec-isconcatspreadable description: Revoked proxy value produces a TypeError when supplied to IsArray info: | [...] 5. Repeat, while items is not empty a. Remove the first element from items and let E be the value of the element. b. Let spreadable be ? IsConcatSpreadable(E). c. If spreadable is true, then [...] e. Else E is added as a single item rather than spread, [...] ES6 22.1.3.1.1: Runtime Semantics: IsConcatSpreadable ( O ) 1. If Type(O) is not Object, return false. 2. Let spreadable be ? Get(O, @@isConcatSpreadable). 3. If spreadable is not undefined, return ToBoolean(spreadable). 4. Return ? IsArray(O). 7.2.2 IsArray [...] 3. If argument is a Proxy exotic object, then a. If the value of the [[ProxyHandler]] internal slot of argument is null, throw a TypeError exception. b. Let target be the value of the [[ProxyTarget]] internal slot of argument. c. Return ? IsArray(target). features: [Proxy, Symbol.isConcatSpreadable] ---*/ var target = []; var handle = Proxy.revocable(target, { get: function(_, key) { // Defer proxy revocation until after property access to ensure that the // expected TypeError originates from the IsArray operation. if (key === Symbol.isConcatSpreadable) { handle.revoke(); } return target[key]; } }); assert.throws(TypeError, function() { [].concat(handle.proxy); }, '[].concat(handle.proxy) throws a TypeError exception');