I'm a newbie in node js Development. I just learn node js in short time ago. Here I create a router file
import express from 'express';
import storyController from '../../controllers/story';
const router = express.Router();
router.post('/', (req, res) => {
const { author, title } = req.body;
console.log(author);
const story = {
author: req.body.author,
title: req.body.title,
content: req.body.content,
tags: req.body.tags
};
storyController.createStory(story, function(error, result){
console.log("halo");
if(error)
res.status(500).send({ success: false, message: error.message});
res.status(200).send({ success: true, message: "Success"});
});
});
Then, i create one more file referred as the controller here
import mongoose from 'mongoose';
const Story = mongoose.model('Story');
exports.createStory = async (story) => {
const { author, title } = story;
if(!author){
console.log("hahaAuthor");
return {
error: true,
message: 'You must write an author name!'
};
}
if(!title) {
console.log("haha");
return {
error: true,
message: 'You must write a title!'
}
}
const newStory = new Story({
author: author,
title: title,
content: story.content,
tags: story.tags,
slug: ''
});
newStory.save().then((story) => {
return { error: false, result: story};
}).catch((error) => {
return { error: error};
})
};
But, unfortunately I don't know why my function in router file doesn't call the callback function. The console.log doesn't even called yet. Please help. Otherwise, maybe you have a better way to do this. Thanks!
As createStory is an async function. Change your code like this. You are mixing async with Promise and callback
exports.createStory = async (story) => {
...
// Change the promise to await
let story = await newStory.save();
return { error: false, result: story};
};
Error should be handled in the controller with Promise catch clause.
Something like
router.post('/', (req, res) => {
storyController.createStory.then(data => {
return res.json({error: false, data: data});
}).catch(e => {
return res.json({error: true});
})
});
Note: Either use callback or async. async is the best option now adays
May be this can work:
// 1. callback style
newStory.save().then((story) => {
return cb(null, story);
}).catch((error) => {
return cb(error);
})
// 2. await
await newStory.save();
// controller
router.post('/', (req, res) => {
storyController.createStory.then(data => {
return res.json(...);
}).catch(e => {
return res.json(...);
});
If you use callback style, Error-First Callback is better.
Related
I am using the package "fcm-node" in order to send notifications to certain device id.
the sendNotification function is as follows:
const FCM = require('fcm-node');
const serverKey = process.env.SERVER_KEY;
const fcm = new FCM(serverKey);
function sendNotification(registrationToken, title, body, type, key) {
const message = {
to: registrationToken,
collapse_key: key,
notification: {
title: title,
body: body,
delivery_receipt_requested: true,
sound: `ping.aiff`
},
data: {
type: type,
my_key: key,
}
};
fcm.send(message, function (err, value) {
if (err) {
console.log(err);
return false;
} else {
console.log(value);
return value;
}
});
};
module.exports = {
sendNotification
};
The api function I use to call this function is as follows:
router.get('/test', async (req, res, next) => {
const promise = new Promise((resolve, reject) => {
let data = sendNotification('', 'dfsa', 'asds', 'dfas', 'afsdf');
console.log(data)
if (data == false) reject(data);
else resolve(data);
});
promise
.then((data) => { return res.status(200).send(data); })
.catch((data) => { return res.status(500).send(data) })
});
When I console.log the "err" and "value" from the sendNotification, I get either of the followings:
{"multicast_id":4488027446433525506,"success":1,"failure":0,"canonical_ids":0,"results":[{"message_id":"0:1652082785265643%557c6f39557c6f39"}]};
{"multicast_id":8241007545302148303,"success":0,"failure":1,"canonical_ids":0,"results":[{"error":"InvalidRegistration"}]}
In case it is successful, I made sure that the device is receiving the notification.
The problem is in the api's data. It is always "undefined" and weither send notification is successful or not I get the 200 Ok status.
What seems to be the problem?
You can't return anything from the function (err, value) {} callback of a node-style asynchrnous function.
Your sendNotification() function needs to return a promise. util.promisify() makes the conversion from a node-style asynchronous function to a promise-returning asynchronous function convenient. Note the return, it's important:
const FCM = require('fcm-node');
const serverKey = process.env.SERVER_KEY;
const fcm = new FCM(serverKey);
const { promisify } = require('util');
fcm.sendAsync = promisify(fcm.send);
function sendNotification(registrationToken, title, body, type, key) {
return fcm.sendAsync({
to: registrationToken,
collapse_key: key,
notification: {
title: title,
body: body,
delivery_receipt_requested: true,
sound: `ping.aiff`
},
data: {
type: type,
my_key: key,
}
});
}
module.exports = {
sendNotification
};
Now you can do what you had in mind
router.get('/test', async (req, res, next) => {
try {
const data = await sendNotification('', 'dfsa', 'asds', 'dfas', 'afsdf');
return res.status(200).send(data);
} catch (err) {
return res.status(500).send(err);
}
});
Maybe it will help, at first try to return your response (the promise) in sendNotification, as actually you have a void function, that's why it's always undefined and after in your route
router.get('/test', async (req, res, next) => {
try {
const data = sendNotification('', 'dfsa', 'asds', 'dfas', 'afsdf');
if (data) {
return res.status(200).send(data);
}
} catch(err) {
return res.status(500).send(err);
}
});
Having issues with using async and await. I'm executing two queries and then saving the result to a temp variable. After I have collected the response from all executed queries, I'm going to send that to the client.
Here is my current example code.
module.exports = (app) => {
app.get('/api/stats', (req, res) => {
let fetch1 = '';
let fetch2 = '';
conn.query('query here', [], async (error, results) => {
if (error) {
return res.send({
success: false,
message: 'There was an error.'
});
} else {
fetch1 = results;
}
});
conn.query('query here', [], async (error, results) => {
if (error) {
return res.send({
success: false,
message: 'There was an error.'
});
} else {
fetch2 = results;
}
});
// I need to wait until the queries have resolved so that I can send the correct data
return res.send({
success: true,
fetch1: fetch1,
fetch2: fetch2
});
});
};
I basically need to wait until the queries have been resolved so that I can send the correct data towards the end.
Can anyone explain how I can use await and async to accomplish this?
Thanks.
You can only await a Promise, so for functions that don't return Promises you need to create a Promise wrapper. This needs to be done per call that would previously use a callback, but you can make a helper function per function you need to wrap.
function queryPromise(query, parameters) {
return new Promise((resolve, reject) => {
conn.query(query, parameters, (err, results) => {
if(err) {
reject(err);
} else {
resolve(results);
}
});
});
}
module.exports = (app) => {
app.get('/api/stats', async (req, res) => {
try {
let fetch1 = await queryPromise('query here', []);
let fetch2 = await queryPromise('query here', []);
res.send({
success: true,
fetch1: fetch1,
fetch2: fetch2
});
} catch {
res.send({
success: false,
message: 'There was an error.'
});
}
});
};
From my knowledge, I usually apply async to functions and perform await on certain variables (inside the function) that need to be acquired from a specific database.
So to implement this into your function containing the async tag, you could possibly do:
fetch1 = await results;
fetch2 = await results;
This will wait until the data is attached onto the variable fetch1 and fetch2 before continuing on with the code.
Sorry if this was very vague, hopefully this was somewhat helpful.
I have a method that deletes products and before it does it check if the user who is trying to delete the product is the user who created it. When i execute it with Insomnia it successfully removes the product but i get an error on the console saying cannot set headers after they are sent to the client.
My method:
exports.deleteProduct = (req, res) => {
const id = req.params.productId;
Product.deleteOne({ _id: id, userId: req.user._id }, () => {
return res.status(401).json("Not authorized");
})
.then(() => {
return res.status(200).json("Product deleted");
})
.catch((err) => {
return res.status(500).json({
error: err,
});
});
};
I'm pretty sure this is happening because I'm chaining a .then() and .catch() after executing it.
I tried to do this but it didn't work because the err parameter that I'm sending to the callback function is null.:
exports.deleteProduct = (req, res) => {
const id = req.params.productId;
Product.deleteOne({ _id: id, userId: req.user._id }, (err) => {
if (err) {
return res.status(401).json("Not authorized");
}
return res.status(200).json("Product deleted");
});
};
When i tried this second approach I always got the 200 status, meanwhile the product didn't delete.
Any idea how to deal with this?
You can try something like this:
Product.deleteOne({ _id: id, userId: req.user._id }, (err, result) => {
if(err) {
return "something"
}
return "something else"
});
or: in async / await way
try {
await Product.deleteOne({ _id: id, userId: req.user._id });
} catch (err) {
// handle error here
}
By the way, why you are passing userId at the deleteOne method?
How would I structure a function that has multiple Mongoose.findOne() nested in each other?
I need to do something like
const userId = '...';
const postId = '...';
const imageId = '...';
User.findById(userId).then(user => {
if (!user) {
return res.status(400).json({
status: 'error',
err: 'User not found',
});
}
Post.findById(postId).then(post => {
if (!post) {
return res.status(400).json({
status: 'error',
err: 'Post not found',
});
}
Image.findById(imageId).then(image => {
if (!image) {
return res.status(400).json({
status: 'error',
err: 'Image not found',
});
// DO SOMETHING WITH VARIABLES 'user', 'post', AND 'image'
}).catch(err => { .. });
}).catch(err => { .. });
}).catch(err => { .. });
Since Collection.findById() returns a promise, I guess I should use chaining instead of this structure.
So it might be something like
User
.findById(userId)
.then(user => Post.findById(postId))
.then(post => Image.findById(imageId))
.then(image => {
// DO SOMETHING WITH VARIABLES 'user', 'post', AND 'image'
});
.catch(err => { .. });
but I don't know how to access the variables user, post, and image, and how to throw the errors, so I can access them in my catch statement.
Edit
I have tried this
async function getPostAsync() {
const userId = '597989c668189f31483ffdbf';
const postId = '597989c62624ea74750c74f8';
if (!userId) {
throw new Error('User id missing');
}
if (!postId) {
throw new Error('Post id missing');
}
const user = await User.findById(userId);
const post = await Post.findById(postId);
return post;
}
app.get('/', (req, res) => {
getPostAsync().then(post => {
res.json({
status: 'success',
});
}).catch(err => {
res.status(400).json({
status: 'error',
err
});
})
});
but I just receive
{
"status": "error",
"err": {}
}
Am I doing something wrong?
But I get the same result even with
async function getPostAsync() {
throw new Error('msg');
return Post.find();
}
so I might be calling the async function wrong.
You can use Promise.all:
Promise.all([
User.findById(userId),
Post.findById(postId),
Image.findById(imageId)
])
.then(result)=>{
let user = result[0];
let post = result[1];
let image = result[2];
})
.catch(err => { .. });
Or with destructing assignment:
Promise.all([
User.findById(userId),
Post.findById(postId),
Image.findById(imageId)
])
.then(([user, post, image])=>{...})
.catch(err => { .. });
You can't access those variables inside a later promise's then, but you can get round it by assigning the local resolved values to global variables
let globalUser, globalPost; // create variables for later
User
.findById(userId)
.then(user => {
globalUser = user; // assign to global
return Post.findById(postId)
})
.then(post => {
globalPost = post; // assign to global
return Image.findById(imageId)
})
.then(image => {
// DO SOMETHING WITH VARIABLES 'globalUser', 'globalPost', AND 'image'
})
.catch(err => {... });
EDIT: or when using async/await:
async function() {
const user = await User.findById(userId);
const post = await Post.findById(postId);
const image = await Image.findById(imageId);
// do something with user, post and image
}
Seeing as your promises don't rely on each other you could also use Promise.all() in an async function:
async function() {
const result = await Promise.all([
User.findById(userId),
Post.findById(postId),
Image.findById(imageId)
]);
const [user, post, image] = result;
// do something with user, post and image
}
EDIT 2: Error handling
async function getImage() {
let user;
try {
user = await User.findById(userId);
} catch (error) { // deal with rejection of `User.findById`
// do something with error
}
// if these fail the entire function will throw
const post = await Post.findById(postId);
const image = await Image.findById(imageId);
return image;
}
getImage()
.then(image => {... })
.catch(error => {... }); // deal with rejection of `getImage` as a whole
The above code showcases the ways you can handle errors in an async function. The first is how we deal with an error in the User.findById function, by simply wrapping it in a try catch block.
The second method is by simply letting the entire async function throw an error. I.e. if the Post.findById or Image.findById promises reject, the entire getImage() promise will reject, which you can deal with in the .catch() handler.
I've got a route using Sequelize.js
app.get('/api/users/:username', (req, res) => {
const foundUser = getUserByUsername(req.params.username);
console.log(`foundUser = ${foundUser}`);
return res.send(foundUser);
});
the getUserByUsername function is as follows
const getUserByUsername = username => {
Viewer.findOne({
where: {username}
}).then(response => {
console.log(response.dataValues);//the object with the data I need
return response.dataValues;
});
};
I hoped on getting the object in my const foundUser in my route, but it seems I need to wait until the findOne has been executed, because in my console I can see that the log of foundUser (which is undefined then) is executed before the function getUserByUsername
foundUser = undefined
Executing (default): SELECT `id`, `username`, `instakluiten`, `role`, `createdAt`, `updatedAt` FROM `viewers` AS `viewer` WHERE `viewer`.`username` = 'instak' LIMIT 1;
{ id: 19,
username: 'instak',
instakluiten: 18550,
role: 'moderators',
createdAt: 2016-10-02T16:27:44.000Z,
updatedAt: 2016-10-09T10:17:40.000Z }
How can I make sure that my foundUser will be updated with the data áfter the user has been found?
You have to return the promise that Sequelize creates and then wait for it to resolve. So the getUserByUsername becomes:
const getUserByUsername = username => {
return Viewer.findOne({
where: {username}
}).then(response => {
console.log(response.dataValues);//the object with the data I need
return response.dataValues;
});
};
and in the route:
app.get('/api/users/:username', (req, res) => {
getUserByUsername(req.params.username).then(foundUser => {
res.send(foundUser);
});
});
This is because you need to keep the chain of promises. If you forget to return it, the function returns undefined end even if the promise is finallly resolved, the value it resolves to never gets up back in the chain.
app.get('/api/users/:username', (req, res) => {
getUserByUsername(req.params.username, function(err, result){
const foundUser = result;
console.log(`foundUser = ${foundUser}`);
res.send(foundUser);
});
});
const getUserByUsername = function(username, callback) {
Viewer.findOne({
where: {username}
}).then(response => {
console.log(response.dataValues);//the object with the data I need
return callback(null, response.dataValues);
});
};
You can avoid it with promise or with callback
app.get('/api/users/:username', (req, res) => {
getUserByUsername(req.params.username, function(err, foundUser) {
if (!err) {
console.log(`foundUser = ${foundUser}`);
return res.send(foundUser);
} else {
res.send(err)
}
});
});
const getUserByUsername = (username, callback) => {
Viewer.findOne({
where: {
username
}
}).then(response => {
console.log(response.dataValues); //the object with the data I need
return callback(null, response.dataValues);
});
};