emulates-undefined.js (1347B)
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. Let r be the result of performing Abstract Equality Comparison rval == lval. 12 6. ReturnIfAbrupt(r). 13 7. If r is true, return false. Otherwise, return true. 14 15 The [[IsHTMLDDA]] Internal Slot / Changes to Abstract Equality Comparison 16 17 The following steps are inserted after step 3 of the Abstract Equality Comparison algorithm: 18 19 1. If Type(x) is Object and x has an [[IsHTMLDDA]] internal slot and y is either null or undefined, return true. 20 2. If x is either null or undefined and Type(y) is Object and y has an [[IsHTMLDDA]] internal slot, return true. 21 features: [IsHTMLDDA] 22 ---*/ 23 24 var IsHTMLDDA = $262.IsHTMLDDA; 25 26 assert.sameValue(IsHTMLDDA != undefined, false, "!= with `undefined`"); 27 assert.sameValue(undefined != IsHTMLDDA, false, "!= with `undefined`"); 28 29 assert.sameValue(IsHTMLDDA != null, false, "!= with `null`"); 30 assert.sameValue(null != IsHTMLDDA, false, "!= with `null`"); 31 32 assert.sameValue(IsHTMLDDA != IsHTMLDDA, false); 33 34 reportCompare(0, 0);