1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
|
// Copyright (C) 2019 Leo Balter. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.
/*---
description: >
Short circuit if the CoalesceExpressionHead is not undefined or null (the empty string)
esid: sec-conditional-operator
info: |
ConditionalExpression :
ShortCircuitExpression
ShortCircuitExpression ? AssignmentExpression : AssignmentExpression
ShortCircuitExpression :
LogicalORExpression
CoalesceExpression
CoalesceExpression :
CoalesceExpressionHead ?? BitwiseORExpression
CoalesceExpressionHead :
CoalesceExpression
BitwiseORExpression
Runtime Semantics: Evaluation
CoalesceExpression:CoalesceExpressionHead??BitwiseORExpression
1. Let lref be the result of evaluating CoalesceExpressionHead.
2. Let lval be ? GetValue(lref).
3. If lval is undefined or null,
a. Let rref be the result of evaluating BitwiseORExpression.
b. Return ? GetValue(rref).
4. Otherwise, return lval.
features: [coalesce-expression]
---*/
var x;
var str = '';
x = undefined;
x = str ?? 1;
assert.sameValue(x, str, 'str ?? 1');
x = undefined;
x = str ?? null;
assert.sameValue(x, str, 'str ?? null');
x = undefined;
x = str ?? undefined;
assert.sameValue(x, str, 'str ?? undefined');
x = undefined;
x = str ?? null ?? undefined;
assert.sameValue(x, str, 'str ?? null ?? undefined');
x = undefined;
x = str ?? undefined ?? null;
assert.sameValue(x, str, 'str ?? undefined ?? null');
x = undefined;
x = str ?? null ?? null;
assert.sameValue(x, str, 'str ?? null ?? null');
x = undefined;
x = str ?? undefined ?? undefined;
assert.sameValue(x, str, 'str ?? null ?? null');
x = undefined;
x = null ?? str ?? null;
assert.sameValue(x, str, 'null ?? str ?? null');
x = undefined;
x = null ?? str ?? undefined;
assert.sameValue(x, str, 'null ?? str ?? undefined');
x = undefined;
x = undefined ?? str ?? null;
assert.sameValue(x, str, 'undefined ?? str ?? null');
x = undefined;
x = undefined ?? str ?? undefined;
assert.sameValue(x, str, 'undefined ?? str ?? undefined');
|
