質問編集履歴
2
仮変数名変更resolve⇒func
test
CHANGED
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File without changes
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test
CHANGED
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@@ -134,11 +134,11 @@
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134
134
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135
135
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const psvar = [];
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136
136
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137
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-
const doSetTimeout = (
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137
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+
const doSetTimeout = (func, i) => {
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138
138
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139
139
|
setTimeout(() => {
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140
140
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141
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-
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141
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+
func(i);
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142
142
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143
143
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}, 0);
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144
144
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|
1
setTimeoutを外部で宣言すると出力結果が変わる
test
CHANGED
|
File without changes
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test
CHANGED
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@@ -79,3 +79,85 @@
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79
79
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});
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80
80
|
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81
81
|
```
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|
82
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+
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|
83
|
+
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|
84
|
+
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85
|
+
↓編集により追記しました
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86
|
+
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87
|
+
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88
|
+
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|
89
|
+
setTimeoutを外部で宣言すると、
|
|
90
|
+
|
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91
|
+
index変数iの宣言がvarでも
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|
92
|
+
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|
93
|
+
期待通りの出力[ 0, 1, 2, 3, 4 ]になることを発見しました。
|
|
94
|
+
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|
95
|
+
これも、なぜなのでしょうか。
|
|
96
|
+
|
|
97
|
+
|
|
98
|
+
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|
99
|
+
```JavaScript
|
|
100
|
+
|
|
101
|
+
const ps = [];
|
|
102
|
+
|
|
103
|
+
const getPromise = (i) => {
|
|
104
|
+
|
|
105
|
+
return new Promise(resolve => {
|
|
106
|
+
|
|
107
|
+
setTimeout(() => {
|
|
108
|
+
|
|
109
|
+
resolve(i);
|
|
110
|
+
|
|
111
|
+
}, 0);
|
|
112
|
+
|
|
113
|
+
});
|
|
114
|
+
|
|
115
|
+
};
|
|
116
|
+
|
|
117
|
+
for (var i = 0; i < 5; i++) {
|
|
118
|
+
|
|
119
|
+
ps.push(getPromise(i));
|
|
120
|
+
|
|
121
|
+
}
|
|
122
|
+
|
|
123
|
+
Promise.all(ps).then(results => {
|
|
124
|
+
|
|
125
|
+
console.log(results); // [ 0, 1, 2, 3, 4 ]
|
|
126
|
+
|
|
127
|
+
});
|
|
128
|
+
|
|
129
|
+
```
|
|
130
|
+
|
|
131
|
+
|
|
132
|
+
|
|
133
|
+
```JavaScript
|
|
134
|
+
|
|
135
|
+
const psvar = [];
|
|
136
|
+
|
|
137
|
+
const doSetTimeout = (resolve, i) => {
|
|
138
|
+
|
|
139
|
+
setTimeout(() => {
|
|
140
|
+
|
|
141
|
+
resolve(i);
|
|
142
|
+
|
|
143
|
+
}, 0);
|
|
144
|
+
|
|
145
|
+
};
|
|
146
|
+
|
|
147
|
+
for (var i = 0; i < 5; i++) {
|
|
148
|
+
|
|
149
|
+
psvar.push(new Promise(resolve => {
|
|
150
|
+
|
|
151
|
+
doSetTimeout(resolve, i);
|
|
152
|
+
|
|
153
|
+
}));
|
|
154
|
+
|
|
155
|
+
}
|
|
156
|
+
|
|
157
|
+
Promise.all(psvar).then(results => {
|
|
158
|
+
|
|
159
|
+
console.log(results); // [ 0, 1, 2, 3, 4 ]
|
|
160
|
+
|
|
161
|
+
});
|
|
162
|
+
|
|
163
|
+
```
|