emulates-undefined.js (1179B)
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-equality-operators-runtime-semantics-evaluation 5 description: > 6 Abstract Equality special-cases [[IsHTMLDDA]] objects with `undefined` and `null`. 7 info: | 8 EqualityExpression : EqualityExpression == RelationalExpression 9 10 [...] 11 5. Return the result of performing Abstract Equality Comparison rval == lval. 12 13 The [[IsHTMLDDA]] Internal Slot / Changes to Abstract Equality Comparison 14 15 The following steps are inserted after step 3 of the Abstract Equality Comparison algorithm: 16 17 1. If Type(x) is Object and x has an [[IsHTMLDDA]] internal slot and y is either null or undefined, return true. 18 2. If x is either null or undefined and Type(y) is Object and y has an [[IsHTMLDDA]] internal slot, return true. 19 features: [IsHTMLDDA] 20 ---*/ 21 22 var IsHTMLDDA = $262.IsHTMLDDA; 23 24 assert(IsHTMLDDA == undefined, "== with `undefined`"); 25 assert(undefined == IsHTMLDDA, "== with `undefined`"); 26 27 assert(IsHTMLDDA == null, "== with `null`"); 28 assert(null == IsHTMLDDA, "== with `null`"); 29 30 assert(IsHTMLDDA == IsHTMLDDA); 31 32 reportCompare(0, 0);