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トップに関する質問コールバック関数内から値を返す方法

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7

コード修正

2020/08/12 07:21

投稿

kawauso
kawauso

スコア56

test CHANGED
File without changes
test CHANGED
@@ -21,8 +21,6 @@
21
21
  ### 該当のソースコード
22
22
 
23
23
  修正1
24
-
25
- result.resolveにはundefined
26
24
 
27
25
  ```javascript
28
26
 
@@ -54,13 +52,13 @@
54
52
 
55
53
  await connection.query(query, (err, rows, fields) => {
56
54
 
57
- result = Boolean(rows[0].result);
55
+ result = Boolean(rows[0].result); // ★3番目に呼ばれる
58
56
 
59
57
  });
60
58
 
61
59
 
62
60
 
63
- return result;
61
+ return result; // ★1番目に呼ばれる
64
62
 
65
63
  }
66
64
 
@@ -68,81 +66,13 @@
68
66
 
69
67
  // 呼び出し元
70
68
 
71
- http.createServer(function (req, res) {
69
+ http.createServer(async function (req, res) {
72
70
 
73
71
  if (req.method == 'POST') {
74
72
 
75
- var result = isRegistered('hogehoge');
73
+ var result = awit isRegistered('hogehoge');
76
74
 
77
- console.log(result.resolve);
75
+ console.log(result.resolve);// ★2番目に呼ばれる
78
-
79
- }
80
-
81
- }).listen(8080);
82
-
83
- ```
84
-
85
-
86
-
87
- 修正2
88
-
89
- resultはundefined
90
-
91
- ```javascript
92
-
93
- var http = require('http');
94
-
95
- const mysql = require('mysql');
96
-
97
- var result;
98
-
99
-
100
-
101
- const connection = mysql.createConnection({
102
-
103
- host: '',
104
-
105
- user: 'aaa',
106
-
107
- password: 'bbb',
108
-
109
- port: '3306'
110
-
111
- });
112
-
113
-
114
-
115
- function isRegistered(id) {
116
-
117
- var result = false;
118
-
119
-
120
-
121
- var query = `SELECT EXISTS (SELECT * FROM hoges WHERE id = '${id}') as result;`;
122
-
123
- connection.query(query, (err, rows, fields) => {
124
-
125
- result = Boolean(rows[0].result);
126
-
127
- });
128
-
129
-
130
-
131
- return result;
132
-
133
- }
134
-
135
-
136
-
137
- // 呼び出し元
138
-
139
- http.createServer(function (req, res) {
140
-
141
- if (req.method == 'POST') {
142
-
143
- isRegistered('hogehoge');
144
-
145
- console.log(result);
146
76
 
147
77
  }
148
78
 

6

修正

2020/08/12 07:21

投稿

kawauso
kawauso

スコア56

test CHANGED
File without changes
test CHANGED
@@ -22,7 +22,7 @@
22
22
 
23
23
  修正1
24
24
 
25
- resultにはtrueのみ
25
+ result.resolveにはundefined
26
26
 
27
27
  ```javascript
28
28
 
@@ -74,7 +74,7 @@
74
74
 
75
75
  var result = isRegistered('hogehoge');
76
76
 
77
- console.log(result);
77
+ console.log(result.resolve);
78
78
 
79
79
  }
80
80
 

5

コード修正

2020/08/12 06:49

投稿

kawauso
kawauso

スコア56

test CHANGED
File without changes
test CHANGED
@@ -72,7 +72,9 @@
72
72
 
73
73
  if (req.method == 'POST') {
74
74
 
75
- var result = db.isRegistered('hogehoge');
75
+ var result = isRegistered('hogehoge');
76
+
77
+ console.log(result);
76
78
 
77
79
  }
78
80
 
@@ -138,7 +140,9 @@
138
140
 
139
141
  if (req.method == 'POST') {
140
142
 
141
- var result = db.isRegistered('hogehoge');
143
+ isRegistered('hogehoge');
144
+
145
+ console.log(result);
142
146
 
143
147
  }
144
148
 

4

回答を受けてコード修正

2020/08/12 06:27

投稿

kawauso
kawauso

スコア56

test CHANGED
File without changes
test CHANGED
@@ -20,7 +20,9 @@
20
20
 
21
21
  ### 該当のソースコード
22
22
 
23
+ 修正1
23
24
 
25
+ resultにはtrueのみ
24
26
 
25
27
  ```javascript
26
28
 
@@ -80,6 +82,72 @@
80
82
 
81
83
 
82
84
 
85
+ 修正2
86
+
87
+ resultはundefined
88
+
89
+ ```javascript
90
+
91
+ var http = require('http');
92
+
93
+ const mysql = require('mysql');
94
+
95
+ var result;
96
+
97
+
98
+
99
+ const connection = mysql.createConnection({
100
+
101
+ host: '',
102
+
103
+ user: 'aaa',
104
+
105
+ password: 'bbb',
106
+
107
+ port: '3306'
108
+
109
+ });
110
+
111
+
112
+
113
+ function isRegistered(id) {
114
+
115
+ var result = false;
116
+
117
+
118
+
119
+ var query = `SELECT EXISTS (SELECT * FROM hoges WHERE id = '${id}') as result;`;
120
+
121
+ connection.query(query, (err, rows, fields) => {
122
+
123
+ result = Boolean(rows[0].result);
124
+
125
+ });
126
+
127
+
128
+
129
+ return result;
130
+
131
+ }
132
+
133
+
134
+
135
+ // 呼び出し元
136
+
137
+ http.createServer(function (req, res) {
138
+
139
+ if (req.method == 'POST') {
140
+
141
+ var result = db.isRegistered('hogehoge');
142
+
143
+ }
144
+
145
+ }).listen(8080);
146
+
147
+ ```
148
+
149
+
150
+
83
151
  ### 試したこと
84
152
 
85
153
 

3

コード修正

2020/08/12 06:25

投稿

kawauso
kawauso

スコア56

test CHANGED
File without changes
test CHANGED
@@ -24,6 +24,8 @@
24
24
 
25
25
  ```javascript
26
26
 
27
+ var http = require('http');
28
+
27
29
  const mysql = require('mysql');
28
30
 
29
31
  const connection = mysql.createConnection({
@@ -40,7 +42,7 @@
40
42
 
41
43
 
42
44
 
43
- function isRegistered(id) {
45
+ async function isRegistered(id) {
44
46
 
45
47
  var result = false;
46
48
 
@@ -48,7 +50,7 @@
48
50
 
49
51
  var query = `SELECT EXISTS (SELECT * FROM hoges WHERE id = '${id}') as result;`;
50
52
 
51
- connection.query(query, (err, rows, fields) => {
53
+ await connection.query(query, (err, rows, fields) => {
52
54
 
53
55
  result = Boolean(rows[0].result);
54
56
 
@@ -59,6 +61,20 @@
59
61
  return result;
60
62
 
61
63
  }
64
+
65
+
66
+
67
+ // 呼び出し元
68
+
69
+ http.createServer(function (req, res) {
70
+
71
+ if (req.method == 'POST') {
72
+
73
+ var result = db.isRegistered('hogehoge');
74
+
75
+ }
76
+
77
+ }).listen(8080);
62
78
 
63
79
  ```
64
80
 

2

コード修正

2020/08/12 06:17

投稿

kawauso
kawauso

スコア56

test CHANGED
File without changes
test CHANGED
@@ -23,6 +23,8 @@
23
23
 
24
24
 
25
25
  ```javascript
26
+
27
+ const mysql = require('mysql');
26
28
 
27
29
  const connection = mysql.createConnection({
28
30
 

1

コード追記

2020/08/12 05:57

投稿

kawauso
kawauso

スコア56

test CHANGED
File without changes
test CHANGED
@@ -23,6 +23,20 @@
23
23
 
24
24
 
25
25
  ```javascript
26
+
27
+ const connection = mysql.createConnection({
28
+
29
+ host: '',
30
+
31
+ user: 'aaa',
32
+
33
+ password: 'bbb',
34
+
35
+ port: '3306'
36
+
37
+ });
38
+
39
+
26
40
 
27
41
  function isRegistered(id) {
28
42