object-pattern-emulates-undefined.js (1086B)
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 esid: sec-destructuring-binding-patterns-runtime-semantics-bindinginitialization 5 description: > 6 Destructuring initializer is not evaluated when value is an object 7 with [[IsHTMLDDA]] internal slot. 8 info: | 9 BindingPattern : ObjectBindingPattern 10 11 1. Perform ? RequireObjectCoercible(value). 12 2. Return the result of performing BindingInitialization for 13 ObjectBindingPattern using value and environment as arguments. 14 15 Runtime Semantics: KeyedBindingInitialization 16 17 SingleNameBinding : BindingIdentifier Initializer[opt] 18 19 [...] 20 4. If Initializer is present and v is undefined, then 21 [...] 22 5. If environment is undefined, return ? PutValue(lhs, v). 23 features: [destructuring-binding, IsHTMLDDA] 24 ---*/ 25 26 let initCount = 0; 27 const counter = function() { 28 initCount += 1; 29 }; 30 31 const IsHTMLDDA = $262.IsHTMLDDA; 32 const {x = counter()} = {x: IsHTMLDDA}; 33 34 assert.sameValue(x, IsHTMLDDA); 35 assert.sameValue(initCount, 0); 36 37 reportCompare(0, 0);