follows-undefined.js (1406B)
1 // Copyright (C) 2019 Leo Balter. All rights reserved. 2 // This code is governed by the BSD license found in the LICENSE file. 3 4 /*--- 5 description: > 6 If the CoalesceExpressionHead is undefined, follow return the right-side eval. 7 esid: sec-conditional-operator 8 info: | 9 ConditionalExpression : 10 ShortCircuitExpression 11 ShortCircuitExpression ? AssignmentExpression : AssignmentExpression 12 13 ShortCircuitExpression : 14 LogicalORExpression 15 CoalesceExpression 16 17 CoalesceExpression : 18 CoalesceExpressionHead ?? BitwiseORExpression 19 20 CoalesceExpressionHead : 21 CoalesceExpression 22 BitwiseORExpression 23 24 Runtime Semantics: Evaluation 25 26 CoalesceExpression:CoalesceExpressionHead??BitwiseORExpression 27 28 1. Let lref be the result of evaluating CoalesceExpressionHead. 29 2. Let lval be ? GetValue(lref). 30 3. If lval is undefined or null, 31 a. Let rref be the result of evaluating BitwiseORExpression. 32 b. Return ? GetValue(rref). 33 4. Otherwise, return lval. 34 features: [coalesce-expression] 35 ---*/ 36 37 var x; 38 39 x = undefined ?? 42; 40 assert.sameValue(x, 42, 'undefined ?? 42'); 41 42 x = undefined ?? undefined; 43 assert.sameValue(x, undefined, 'undefined ?? undefined'); 44 45 x = undefined ?? null; 46 assert.sameValue(x, null, 'undefined ?? null'); 47 48 x = undefined ?? false; 49 assert.sameValue(x, false, 'undefined ?? false'); 50 51 reportCompare(0, 0);