I live in the PHP world but I am attempting to build out a REST Api using Node.
I have been stuck all day of trying to return an array of results from a for loop. Basically I am passing an array of field_name:field_value. I want to push the result from the update into an array to return. I can get it to log in the console but no further.
Here is a sample post json data
{
"first_name":"Jeff",
"phone":"4855555555"
}
Here is the function and loop
function UpdateKey(user_id, key, value, cb) {
connection.query('UPDATE users SET ' + key + ' = ? WHERE id = ? LIMIT 1', [value, user_id], function(err, results) {
if (err) {
callback = key + " update failed.";
} else {
callback = key + " was updated.";
}
cb(callback);
});
}
for (myKey in post_data) {
UpdateKey(user_id, myKey, post_data[myKey], function(id) {
console.log(id);
});
}
res.send(JSON.stringify({ "status": 200, "error": "", "response": my_results_here }));
I have been researching async but not sure the best route here. Any help would be great!
You could collect all results in an array and send that when the arrays size equals the keys size:
const keys = Object.keys(post_data);
const response = [];
for(const myKey of keys) {
UpdateKey(user_id, myKey, post_data[myKey], function(id) {
response.push(id);
if(keys.length === response.length) {
res.send(JSON.stringify({
status: 200,
error: "",
response
}));
}
});
}
The solution You want:
const updateUserField = (userId, field, value) => {
return Promise((resolve) => {
const query = 'UPDATE users SET ' + field + ' = ? WHERE id = ?';
const data = [value, userId];
connection.query(query, data, (error) => {
if (error) return resolve(field + ' update failed');
resolve(field + ' was updated');
});
});
};
router.post('/user/:id', async (req, res) => {
const userId = req.params.id;
const data = req.body;
const response = [];
for (const field in data) {
response.push(
await updateUserField(userId, field, data[field])
);
}
res.status(200).send({
response
});
});
or in parallel:
router.post('/user/:id', async (req, res) => {
const userId = req.params.id;
const data = req.body;
const response = await Promise.all(
Object
.keys(data)
.map(field => updateUserField(userId, field, data[field]))
);
res.status(200).send({
response
});
});
Correct solution
As I understand You want to get post data and update record in users table.
So why not just do it in one query?
Try this way:
const updateUser = (userId, data) => {
return Promise((resolve, reject) => {
const query = 'UPDATE users SET ? WHERE id = ?';
connection.query(query, [data, userId], (error) => {
if (error) return reject(error);
resolve();
});
});
};
router.post('/user/:id', async (req, res) => {
try {
const userId = req.params.id;
const data = req.body;
await updateUser(userId, data);
res.status(200).send({
message: 'User account successfully updated'
})
}
catch (error) {
console.error(error);
res.status(500).send({
message: 'Failed update user account'
});
}
});
But better think about using ORM i.e. Sequelize for security, validation and etc features that eases dev's life.
Related
I have a sqlite3 database request in my main.js, that is triggered by button click in renderer.js.
The request reaches my main.js. However, I cannot manage to await the results from the database. The issue occurs already in main.js, so I'm stuck even before anything is passed back to the renderer.js.
I hope someone can tell me what I am missing.
Here is my code:
renderer.js
$(document).on('click','#mybtn',function(e){
let query = "SELECT id, name FROM table1"
// send (here is the issue)
window.api.send("db-query", query)
// (next step: receive, might be wrong but not yet my problem)
window.api.receive(channel="receive-db-data", (data) => {
console.log(data);
});
});
main.js
ipcMain.on(channel='db-query', async (e, query) => {
console.log('query received: ' + query);
let data = await db_request(query).then(
function(value) {
console.log('value: ' + value);
return value;
},
function(error) {
console.log('error fetching data from db on query:' + query);
}
)
console.log("response ready: " + data); //returns undefined if 'return value' is used (otherwise nothing)
// to send back to renderer.js later
e.sender.send("db-data", data)
})
let db_request = async (query) => {
let data = []
var sqlite3 = require('sqlite3').verbose();
var dbPath = require('path').resolve(__dirname, '../../Fin.db')
var db = new sqlite3.Database(dbPath)
db.serialize(function(){
db.each(query, function(err, row) {
console.log(row)
data.push({"id": row.id, "name": row.name})
});
});
db.close();
console.log('db_request:' + data)
return data
}
And this is how my terminal looks like:
query received: SELECT id, type, name FROM table1
db_request:
value:
response ready: undefined
{ id: 1, name: 'a' }
{ id: 2, name: 'b' }
{ id: 3, name: 'c' }
You have to convert db_request result to a Promise, and the promise will be resolved when all rows are pushed to the data. When you use the await keyword, there is no need to handle a promise with .then chain.
main.js will look like this:
const sqlite3 = require('sqlite3').verbose();
const dbPath = require('path').resolve(__dirname, '../../Fin.db')
ipcMain.on(channel='db-query', async (e, query) => {
console.log('query received: ' + query)
try {
const data = await db_request(query); // remove .then
console.log('value: ' + data)
// to send back to renderer.js later
e.sender.send("db-data", data)
} catch (error) {
console.log('error fetching data from db on query:' + query);
e.sender.send("db-data", []) // send empty data or error ???
}
})
let db_request = (query) => {
const db = new sqlite3.Database(dbPath)
return new Promise((resolve, reject) => { // return a promise
// I think you dont need serialize for this case
const data = []
db.each(query, (err, row) => {
console.log(err, row)
if (!err) {
data.push({"id": row.id, "name": row.name})
}
}, (error) => {
if (error) {
reject(error)
} else {
resolve(data)
}
});
})
}
i want to fetch data from api and execute for loop to store all response data in mysql database.then again fetch data from api with different request parameter but it does not wait to complete for loop and store data i have tried async/await but noting works
app.get("/api/garudaTx", (req, res) => {
let sql = "SELECT * FROM table_name ORDER BY id ";
let query = conn.query(sql, (err, results) => {
(async function () {
for (let i = 0; i < results.length; i++) {
const element = results[i];
console.log(element.userAddress);
console.log(element.id);
try {
let response = await axios.get(
`https://api.bscscan.com/apimodule=account&action=txlist&address=${element.userAddress}&startblock=1&endblock={blockNo}&sort=asc&apikey=`
);
let last = await (async function () {
console.log(response);
if (response.status != 200 || response.data.result.length == 0) {
let code = response.status.toString();
fs.appendFile("responseError.txt", code + " ", (err) => {
if (err) throw err;
console.log("The lyrics were updated!");
});
fs.appendFile(
"responseError.txt",
element.userAddress + " ",
(err) => {
if (err) throw err;
console.log("The lyrics were updated!");
}
);
}
let body = response.data;
console.log(response.data.result.length);
const promises = [];
for (var index = 0; index < response.data.result.length; index++) {
let data = {
blockNumber: body.result[index].blockNumber,
timeStamp: body.result[index].timeStamp,
hash: body.result[index].hash,
nonce: body.result[index].nonce,
blockHash: body.result[index].blockHash,
from_address: body.result[index].from,
contractAddress: body.result[index].contractAddress,
to_address: body.result[index].to,
value: body.result[index].value,
transactionIndex: body.result[index].transactionIndex,
gas: body.result[index].gas,
gasPrice: body.result[index].gasPrice,
gasUsed: body.result[index].gasUsed,
cumulativeGasUsed: body.result[index].cumulativeGasUsed,
confirmations: body.result[index].confirmations,
};
promises.push(
new Promise((resolve) => {
let sql = "INSERT INTO table_name SET ?";
resolve(
conn.query(sql, data, (err, results) => {
if (err) throw err;
console.log(
JSON.stringify({
status: 200,
error: null,
response: results,
})
);
})
);
})
);
}
await Promise.all(promises);
})();
} catch (err) {
console.log(err);
}
}
})();
});
res.send(JSON.stringify({ status: 200, error: null, response: "success" }));
});
i am executing a for to fetch user details from database then i execute api for each user and saved response data with loop but next api is hitting before saving all data in database it does not wait to complete nested for loop
My backend is consist of Api and DB. When I want to get response from DB I have had delayed output by 1 query.
API (I think api is ok. Start read DB first)
app.post('/api/query', (req, res) => {
console.log(`\n Query input : ${JSON.stringify(req.body)}`);
let queryInput = (Object.values(req.body).join(' '));
if(!dbApi.checkArray(queryInput)){ //If array is not made from clear strings
res.json(dbApi.queryFromUser(queryInput));
}
else{
res.json(dbApi.queryOutput);
}
});
app.listen(dbConfig.server.port, () =>
console.log(`Server running on port ${dbConfig.server.port}`));
DB
queryOutput = [];
const receivingQuery =(queryInput) => {
db.query(queryInput, (err, result) =>{
if(err) throw err+' : '+queryInput;
queryOutput = result;
console.log("\nQuery output "+ JSON.stringify(queryOutput)); //Output (result) is ok
});
return queryOutput //Here is Output from previous query (sends to API)
}
module.exports = {
queryOutput: queryOutput,
queryFromUser: receivingQuery,
}
I tryied callback method and I rewrite it couple of times. But I dont have enough skill to solve it.
If You want to return result of query so simply do following things:
add query method to db module:
function query(sql, args = []) {
return new Promise(function(resolve, reject) {
db.query(sql, args, (err, result) => {
if (err) return reject(err);
resolve(result);
});
});
}
// extra feature, getting user by id
async function getUserById(id) {
const result = await query('SELECT * FROM users WHER id = ? LIMIT 1', [id]);
if (Array.isArray(result) && result[0]) return result[0];
return null;
}
module.exports = {
query,
getUserById, // export user by id
queryOutput,
queryFromUser: receivingQuery,
}
use it (with async and await):
app.post('/api/query', async (req, res) => {
try {
console.log('Query input:', req.body);
const queryInput = Object.values(req.body).join(' ');
const result = await dbApi.query(queryInput);
res.json(result);
}
catch (error) {
console.error(error);
res.status(500).json({message: 'Please try again soon'});
}
});
app.get('/api/users/:id', async (req, res) => {
try {
const user = await dbApi.getUserById(req.params.id);
if (!user) return res.status(404).json({message: 'User not found'});
res.status(200).json(user);
}
catch (error) {
console.error(error);
res.status(500).json({message: 'Please try again soon'});
}
});
app.listen(dbConfig.server.port, () =>
console.log('Server running on port', dbConfig.server.port));
Whenever I hit this api with sending this
[{"project_id": "knsfviv9",
"coach_id": ""
},
{"project_id": "ovsijiov9",
"coach_id": ""
}]
it inserts into database but it gives response 0 as the result variable remains 0. result variable gets incremented but in res.send it sends 0.
can someone help me with this?
app.post('/api/patc/:id', (req, res) => {
let projectList = req.body;
projectList.forEach(element => {
let data = {
patc_id: "patc-" + randomID(),
college_id: req.params.id,
project_id: element.project_id,
coach_id: element.coach_id,
date: NOW()
};
let sql = "INSERT INTO projects_assigned_to_colleges SET ?";
conn.query(sql, data, (err, results) => {
if (err) throw err;
result.push(results);
});
});
res.send(JSON.stringify({ "status": 200, "error": null, "response": result }));
});
You are trying to execute asynchronous code in forEach which is giving you undesired behavior. Change the code to something like this
app.post("/api/patc/:id", async (req, res) => {
let projectList = req.body;
var result = 0;
const result = await Promise.all(projectList.map(element => {
let data = {
patc_id: "patc-" + randomID(),
college_id: req.params.id,
project_id: element.project_id,
coach_id: element.coach_id,
date: NOW()
};
return new Promise((resolve, reject) => {
let sql = "INSERT INTO projects_assigned_to_colleges SET ?";
conn.query(sql, data, (err, results) => {
if (err) throw err;
resolve(results);
});
});
}));
res.send(JSON.stringify({ status: 200, error: null, response: result }));
});
My problem is, I want to make INSERT query for every object from JSON using some loop, but I almost always got an error "Cannot set headers after they are sent to the client".Can someone help?Tnx
const connection = require('./config');
module.exports.excel = function (req, res) {
var _query = 'INSERT INTO excel (id, first_name, last_name) values ?';
var jsonData = req.body;
var values = [];
function database() {
return new Promise((resolve, reject) => {
jsonData.forEach((value) => {
values.push([value.id, value.first_name, value.last_name]);
connection.query(_query, [values], (error, results) => {
if (error) {
reject(
res.json({
status: false,
message: error.message
}))
} else {
resolve(
res.json({
status: true,
data: results,
message: 'Excel file successfully created in database'
}))
}
});
});
})
}
async function write() {
await database();
}
write();
}
After I got JSON from my Angular 6 front I put req.body into jsonData and try with forEach to put every object("value" in this case) into query and write that into Excel file.
You will have to wrap each query in a Promise and wait for all to complete before sending the response using Promise.all
Not that database() is going to throw when one of the queries fail and you won't have any access to the resolved promises.
const connection = require('./config');
module.exports.excel = function(req, res) {
const _query = 'INSERT INTO excel (id, first_name, last_name) values ?';
const jsonData = req.body;
function database() {
return Promise.all(
jsonData.map(
value =>
new Promise((resolve, reject) => {
const values = [value.id, value.first_name, value.last_name]
connection.query(_query, [values], (error, results) => {
if (error) {
reject(error.message);
return;
}
resolve(results);
});
})
)
);
}
async function write() {
try {
const results = await database();
res.json({
status: true,
data: results,
message: 'Excel file successfully created in database'
});
} catch (e) {
res.json({
status: false,
message: e.message
});
}
}
write();
};