Here's a simple script i made:
const Nightmare = require('nightmare');
const sql = require('mssql');
const itens = getRecords();
async function getRecords(){
let itensList = [];
const cfg = {
//config here
};
sql.connect(cfg, function(err){
if(err) console.log(err);
let request = new sql.Request();
request.query("<query here>", (err, result) => {
if(err) console.log(err);
itensList = result;
});
return itensList;
});
}
async function getPrices(){
try{
console.log(itens)
}catch(e){
console.log(e);
}
}
getPrices();
Everything works, but when the getPrices() function gets called, here's what's being logged:
Promise { undefined }
What am i missing here?
request.query is being called, but itenslist is being returned before it can be assigned.
Basically, the order of what is happening is:
request.query is called, and starts running the query.
Since request.query is asynchronous, we move on to the next task - returning itenlist
request.query finishes running, and assigns itenlist the expected value after it has already been returned.
To get your desired functionality, I would recommend using callbacks (which node-mssql supports). Alternatively, you could use the await keyword. For instance:
var queryText = 'SELECT 1 AS Value';
var queryResults = await connection.query(queryText);
Related
I tried to make function for my project in the service. This service need to check is user exists in my database, but my function(this function is checking) inside the class return undefined.
This is my code:
const express = require("express");
const mongoDB = require('mongodb').MongoClient;
const url = "here I paste url to my databse(everything is good here)";
class CheckService {
isUserExists(username) {
mongoDB.connect(url, (error, connection) => {
if (error) {
console.log("Error", '\n', error);
throw error;
}
const query = {name: username};
const db = connection.db("users");
const result = db.collection("users").find(query).toArray(
function findUser(error, result) {
if (error) {
throw error;
}
const arr = [];
if (result.value === arr.value) {
console.log(false);
connection.close();
return false;
} else {
console.log(true);
console.log(arr);
console.log(result);
connection.close();
return true;
}
});
console.log(result);
});
}
}
module.exports = new CheckService();
I imported my service to another service:
const checkService = require('./check.service');
After this, I invoked my function from my service like this:
console.log('function:',checkService.isUserExists(username));
I expected good result, but function doesn't return, that I want, unfortunately.
Please help!
There are two problems with your function
it doesn't return anything
toArray() is a promise, so your console.log probably just prints a promise.
Probably you're looking for something like this:
class CheckService {
async isUserExists(username) {
const connection = await mongoDB.connect(url);
const query = {name: username};
const db = connection.db("users");
const result = await db.collection("users").find(query).toArray();
connection.close();
return result.length !== 0;
}
}
You'd then invoke it with something like
await new CheckService().isUserExists(username);
Though, it's worth noting that you probably don't need toArray and instead could use findOne or even count() since all you care about is existence. I probably also wouldn't instantiate a new connection each time (but that's not super relevant)
2 things wrong here. Firstly the first comment is correct. You're only logging the result and not passing back to the caller. Secondly, a quick peek at the mongo docs shows that retrieval methods are promises. You need to make the function async and add awaits where needed.
Mongo:
https://www.mongodb.com/docs/drivers/node/current/fundamentals/crud/read-operations/retrieve/
Promises:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise
I know this has been asked a lot but I can't seem to use the existing answers to get my code to work. I am trying to use mongojs to make a single query, then put the results in a global (relative to the scope) variable to avoid nesting multiple callbacks. However, I can't seem to get the code to wait for the query to end before continuing.
async function taskmaster() {
const db = mongojs(mongoUri.tasker);
let currentDoc;
const getTask = async function() {
db.tasks.findOne({'task_id': {'$in': [taskId, null]}}, function(err, doc) {
console.log(doc);
currentDoc = doc;
});
}
await getTask();
console.log(currentDoc);
// Code to process currentDoc below
}
No matter what I do, console.log(doc) shows a valid MongoDB document, yet console.log(currentDoc) shows "undefined". Thanks in advance!
Inside your async function, you use findOne method() in callback style, so it's totally normal that console.log(currentDoc) shows undefined, because it executes before
currentDoc = doc;
You can promisify the findOne method, to use it with async/await keyword.
I found a tutorial to promisfy a callback style function here, hope it help : https://flaviocopes.com/node-promisify/
--- EDIT ---
I rewrite your code when promising the findOne method, as suggested by O.Jones
async function taskmaster() {
const getTask = async (taskId) => {
return new Promise((resolve, reject) => {
db.tasks.findOne({'task_id': {'$in': [taskId, null]}}, function(err, doc) {
if(err) {
console.log("problem when retrieve data");
reject(err);
} else {
resolve(doc);
}
});
})
const db = mongojs(mongoUri.tasker);
const currentDoc = await getTask(taskId);
console.log(currentDoc);
}
I need to call out to a function that runs a sql query, with row level functionality, and await the entire process before continuing.
Function code:
const sql = require('mssql')
exports.doit = ()=>{
const pool1 = new sql.ConnectionPool(dbConfig);
const pool1Connect = pool1.connect();
pool1.on('error', err => {
console.error('error occurred on pool')
})
await pool1Connect
try {
const request = pool1.request();
request.stream = true;
request.query('select * from dbo.user');
request.on('row', async orow => {
console.log('outer row');
const innerPool = new sql.ConnectionPool(dbConfig);
const innerConnection = innerPool.connect();
innerPool.on('error', err => {
console.error('error occurred on pool')
});
const iConnection = await innerConnection;
connections.push(iConnection);
const innerRequest = innerPool.request();
innerRequest.stream = true;
var iquery = 'select * from dbo.order where userId='+ orow.userId
innerRequest.query(iquery);
innerRequest.on('row', async irow => {
console.log(`User: ${orow.userId} Order: ${irow.orderId}`);
});
innerRequest.on('done', async () => {
console.log('inner done');
iConnection.close();
});
});
request.on('done', async () => {
console.log('outer done');
})
} catch (err) {
console.error('SQL error', err);
}
sql.on('error', err => {
// ... error handler
})
}
Then call the above function like this:
var doit = require('./testmeHandler.js').doit;
doit()
.then(()=>{
console.log("I AM DONE");
});
OR
await doit();
console.log('I AM DONE');
You get the idea...
But what is really happening is, the function gets called, then 'I AM DONE' and then the results of all the sql calls.
Can someone help me get 'I AM DONE' at the bottom? Still getting used to the async/await and promises.
Thanks
After quite a bit of time trying to get this to work synchronously from the caller I gave up and re-wrote the method to use the regular query (not streaming) and implemented my own paging/throttling as to control memory usage. It works great now!
I am using a connection pool to allow for sub queries and other processes to occur async within a batch of results.
I will post the updated code.
Somehow I believe you have jumbled it all up a bit.
Use this
exports.doit = async ()=>
{
const request = new sql.Request(conn)
let records = await request.query('select * from dbo.user')
records.forEach(async r=>{
try{
// do something
const inner = new sql.Request(conn)
let recordInner = await request.query(innerQuery)
recordInner.forEach(async r=>{//do some stuff})
inner.close()
}
catch(err){
//do something with the error
}
records.close()
})
}
The execution:
async execute(){
const result = await doit()
return result
}
execute()
Though I have no idea why you are using two connections at all . Just try writing a more defined query using JOIN OR WHERE subquery. You can achieve all this in a single query instead of a using nested connection. SQL though a bit old, it really is quite powerful.
select * from dbo.order WHERE userId IN (SELECT userId FROM dbo.user)
Makes more sense to me. But, whatever floats your boat.
More on sub-queries: https://www.dofactory.com/sql/subquery
I am familiar with how to get documents from the Mongo shell, but am having difficulty getting documents using find() when connecting via Node.
What I'm getting right now looks like a lot of cursor info, but not the actual documents.
What do I need to change with the following code so that I get the actual documents logged to the console for 'results'?
const config = require('./../../../configuration');
const url = config.get('MONGO_URL');
const dbName = config.get('MONGO_DATABASE');
const MongoClient = require('mongodb').MongoClient;
const client = new MongoClient(url);
module.exports = async function getSchedules() {
let results;
return new Promise((resolve, reject) => {
client.connect(async function (err) {
if (err) return reject(err);
try {
const db = await client.db(dbName);
results = await db.collection('schedules').find();
} catch (error) {
return reject(error);
}
return resolve(results);
});
});
};
... And here's where I actually try and get the documents:
async function getSchedulesFromDB() {
await getSchedules().then((schedules => {
console.log('schedules: ', schedules); // expect result here
return schedules;
}));
}
When I used this same kind of code structure on a findOne(), it worked. But here when using a find() it is not. What am I missing? Does find() work fundamentally differently than findOne()?
Yes. find() returns a cursor over which you must iterate. findOne() returns a single doc, not a cursor. If you want an array of results, you must "build it yourself" by iterating the cursor, something like:
results = [];
db.collection('schedules').find().forEach(function(d) { results.push(d); });
I'm trying to make a simple api with nodejs. However I can't get nodejs to wait for sql queries to finish.
How can I get nodejs to wait for the queries to finish? Am I using await/async wrong?
The goal here is to only return d after the queries have finished.
Database File
const DB_HOSTNAME = "localhost";
const DB_NAME = "testerino";
const DB_PORT = "8889";
const DB_USERNAME = "root";
const DB_PASSWORD = "root";
const mysql = require('mysql');
const con = mysql.createConnection({
host: DB_HOSTNAME,
user: DB_USERNAME,
password: DB_PASSWORD,
database: DB_NAME,
port: DB_PORT
});
con.connect(function(err) {
if (err) throw err
console.log("Connected to database");
});
async function query(sql){
var results = await con.query(sql);
console.log("foo completed")
return results
}
module.exports = {
con: con,
query: query
}
userLogin File
const db = require('../../common/database');
function attemptUserLogin(usernameOrEmail, password){
var d = {err: [], res: {}};
console.log("attemptUserLogin");
const foo = db.query("SELECT * FROM users");
console.log("This should wait for foo to complete");
return d;
}
module.exports = {
attemptUserLogin: attemptUserLogin
};
Results
Connected to database
attemptUserLogin
This should wait for foo to complete
foo completed
^ it's not waiting
There is no need to use callback with await .Make sure that your con.query() function returns promise ,to you to suceed in this.
async function query(sql){
var results = await con.query(sql); // the result will be stored in results variable ,once the promise is resolved
console.log(results) // the query result will be printed here
return results // the result will be wrapped in promise and returned
}
The above function will return result only when your promise is resolved and the returned data is stored in results variable.
Now if you want to use above function to get the data,you can do it in two ways
1-Use then.
query().then(data=>{
console.log(data) // this variable data holds the value you returned from above query function
})
2-Call the function with await (but you have to do it in async function)
async function other()
{
let query_result=await query(); // it will return the data from query function above
}
See this answer ,I have discussed all possible cases to query data.
Edit -The issue is with your attemptUserLogin function,you have to make it async as well
async function attemptUserLogin(usernameOrEmail, password){
var d = {err: [], res: {}};
console.log("attemptUserLogin");
const foo = await db.query("SELECT * FROM users"); // use await here
console.log(foo);// result from query function above
return d;
}
Revise your execute method like below and put async/await the way I did:
// put async keyword here
const attemptUserLogin = async (usernameOrEmail, password) => {
var d = {err: [], res: {}};
console.log("attemptUserLogin");
// Put await keyword here
const foo = await db.query("SELECT * FROM users");
console.log("This should wait foo.results: ",foo.results);
return d;
}