如何在restapi调用中构造json并使其同步

Question

我试图用nodejs-restapi构建json响应，但我的响应总是提前发送，即使函数尚未执行。

我试着等待并承诺什么都不起作用，然后发送错误。。

//这是我想要的json 结构

[
{
"user_id": "2",
"user_name": "Mehedi Hasan",
"permissions": [
{
"table_name": "questionbank",
"permission_create": "true",
"permission_update": "true",
"permission_delete": "true"
},
{
"table_name": "questionbankquestions",
"permission_create": "true",
"permission_update": "true",
"permission_delete": "true"
},
{
"table_name": "subjects",
"permission_create": "false",
"permission_update": "true",
"permission_delete": "false"
},
{
"table_name": "subjectquestions",
"permission_create": "true",
"permission_update": "true",
"permission_delete": "true"
},
{
"table_name": "modeltests",
"permission_create": "true",
"permission_update": "true",
"permission_delete": "true"
},
{
"table_name": "modeltestquestions",
"permission_create": "true",
"permission_update": "true",
"permission_delete": "true"
}
]
},
............................
]

//这就是我尝试的

function getAllUser(done) {
var sql = "SELECT users.id, users.username FROM users";
db.query(sql, [], function(err, rows, fields) {
if (err) throw err;
done(rows);
});
}
/*--------------------------Check user permission --------------------------*/
router.get("/adminpermissions", function(req, res) {
var sql =
"SELECT table_name, permission_create, permission_update, permission_delete FROM permissions " +
"WHERE user_id = ?";
finalArray = [];
jsonFormat = [];
permissionArray = [];
getAllUser(function(user) {
for (var i = 0; i < user.length; i++) {
userId = user[i].id;
userName = user[i].username;
db.query(sql, [userId], function(err, rows, fields) {
if (err) {
res.status(500).send({ error: "Something failed!" });
}
console.log(rows);
permissionArray[i] = rows;
var data = {
user_id: userId,
user_name: userName,
permission: permissionArray[i]
};
jsonFormat.push(data);
});     
}
res.json(jsonFormat);
});
});

我总是得到[]数组作为响应。。尽管我知道即使循环还没有完成，也会发送响应的问题，但我不知道如何解决。。试着承诺等待，但最终却收到了很多错误消息。。

Answer 1

您可以使用async/await来解决这个问题。你可以这样做：-

router.get("/adminpermissions", function(req, res) {
var sql =
"SELECT table_name, permission_create, permission_update, permission_delete FROM 
permissions " +
"WHERE user_id = ?";
finalArray = [];
jsonFormat = [];
permissionArray = [];
getAllUser(async function(user) {
for (var i = 0; i < user.length; i++) {
userId = user[i].id;
userName = user[i].username;
sql =  "SELECT table_name, permission_create, permission_update, permission_delete 
FROM permissions WHERE user_id = "+  userId;
try {
let result = await db.query(sql)
permissionArray[i] = result[0];
var data = {
user_id: userId,
user_name: userName,
permission: permissionArray[i]
};
jsonFormat.push(data);     
} catch(err) {
res.status(500).send({ error: "Something failed!" });
}
}
res.json(jsonFormat);

})；})；

Answer 2

这就是我所做的，它完美地工作了

/*------------------------ Get Permissions of All User -----------------------------*/
function getAllUser(done) {
var sql = "SELECT users.id, users.username FROM users";
db.query(sql, [], function(err, rows, fields) {
if (err) throw err;
done(rows);
});
}
function getPermission(user_id, user_name,profile_image, done) {
var sql =
"SELECT table_name, permission_create, permission_update, permission_delete FROM permissions " +
"WHERE user_id =?";
db.query(sql, [user_id], function(err, rows, fields) {
if (err) throw err;
done(user_id, user_name, profile_image, rows);
});
}
router.get("/allpermissions", function(req, res) {
var i = 0;
var data = [];
getAllUser(function(user) {
for (i = 0; i < user.length; i++) {
getPermission(user[i].id, user[i].username,user[i].profile_image, function(
userId,
userName,
profileImage,
rows
) {
data.push({
user_id: userId,
user_name: userName,
profile_image: profileImage,
permissions: rows
});
if (data.length == user.length) {
res.json(data);
}
//console.log(data);
});
}
});
});
/*------------------------ ***************************** ---------------------------*/