I need to request X products from another server and I need to wait for that execution to finish before proceeding and saving the order in the database.
Let's say I receive via post an array of product Ids that I need to add to the order, e.g
JSON FILE:
{
"order_products":[1,2,3,4]
}
Here's a code sample:
//Express module
var router = require('express').Router();
//HTTP Request module
var client = require('request');
//Util that saves the URLs of the other databases
var productURL = require('../utils/product/productURL');
//Builds a product object given a JSON
var productBuilder = require('../utils/product/productBuilder');
router.post('/', req, res) {
//Instantiate a new order
var orderInstance = new order({
date: Date.now
});
//Query the products in the other server and add them to the order
req.body.order_products.forEach(id => {
client.get(productURL.HTTPS + id, { json: true }, (err, res, JSONProduct) => {
var product = productBuilder.build(JSONProduct);
orderInstance.order_products.push(product);
});
};
//Save the order in the database
orderInstance.save(....);
//Send response
res.status(201).json(orderInstance);
}
The problem here is that while the loop is still executing, the response is sent (201) and the orderInstance is saved without any product. If I console.log the products they only appear after the orderInstance is saved.
I've tried implementing callbacks to fix this issue, but with no success. I'd appreciate if anyone could lend me a hand here! Thanks in advance :smiley:(edited)
forEach runs synchronously - when the forEach ends, the client.get requests may have all been sent out, but the responses surely haven't come back yet. You need to convert each request into a Promise, and then call Promise.all on an array of those Promises. The Promise.all will resolve once all responses have come back. For example:
const allPromises = req.body.order_products.map(id => new Promise((resolve, reject) => {
client.get('productURL.HTTPS' + id, { json: true }, (err, res, JSONProduct) => {
if (err) reject (err);
else resolve(productBuilder.build(JSONProduct));
});
}));
Promise.all(allPromises)
.then((newProducts) => {
orderInstance.order_products.push(...newProducts);
res.status(201).json(orderInstance);
})
.catch((err) => {
// handle errors
});
Related
I'm trying to get the temperature data from my node.js backend sent to react.js but i kept getting res.send is not a funtion
Sample code here
app.get("/gettemperature", (req, res) => {
const email = req.query.email;
let stmt = `SELECT * FROM users WHERE email=?`;
let todo = [email];
db.query(stmt, todo, (err, results, fields) => {
if (err) {
console.error(err.message);
}
if(results.length > 0 ){
let id = results[0].id;
let getID = `SELECT * FROM controlModules WHERE deviceowner=?`;
let getidData = [id];
db.query(getID, getidData, (err, resulta, fields) => {
if (err) {
console.error(err.message);
}
if(resulta.length > 0){
let lanip = resulta[0].ipaddress;
let url = "http://"+lanip+"/data";
http.get(url,(res) => {
let body = "";
res.on("data", (chunk) => {
body += chunk;
});
res.on("end", () => {
try {
let json = JSON.parse(body);
const temp_actual = json.temperature.value;
console.log(temp_actual);
res.setHeader('Content-Type', 'application/json');
res.end(
JSON.stringify({
value: temp_actual
})
);
} catch (error) {
console.error(error.message);
};
});
}).on("error", (error) => {
console.error(error.message);
});
}
});
}
});
});
i really need to return/send/respond the temperature data to my front end but i'm getting said error, is there a different way to return data?
It looks like you are mixing up an HTTP server you wrote in Node (although you haven't shown any relevant code) and an HTTP client you also wrote in Node.
res is an argument received by the callback you pass to http.get and contains data about the response received by your HTTP client.
Meanwhile, somewhere else (not shown) you have a different variable also called res which is the object your HTTP server uses to send its response to the browser running your React code.
You are calling res.send and wanting res to be the latter but it is really the former.
Since you haven't shown us the HTTP server code, it is hard to say where that res is, but there is a good chance you have shadowed it and can solve your problem by using different names (e.g. client_res and server_res).
That said. I strongly recommend avoiding using the http module directly as the API follows out of date design patterns and isn't very friendly. Consider using fetch or axios for making HTTP requests and Express.js for writing HTTP servers.
I'm new to JavaScript and cannot seem to make this work , the topic of quiz depends on the user input... when the user presses next , I get the topic (this also takes user to the main quiz page), then i have to fetch data from the api with the topic as a parameter... I have to process the result of the fetch operation.. Then I have to pass that info to to the main quiz page... but the variable that is supposed to be populated by the fetch request is still undefined when i pass is to the main quiz page
var Allquestions;
var sheetdb = require('sheetdb-node');
// create a config file
var config = {
address: 'https://sheetdb.io/api/v1/9djmf8ydc7hwy',
};
//sheetdb
// Create new client
var client = sheetdb(config);
function downloadquestions(topic) {
console.log(topic);
client.read({ limit: 2, sheet: topic }).then(function(data) {
console.log(data + " in client.read func")
processQuestions(data);
}, function(err){
console.log(err);
});
}
async function processQuestions(data) {
console.log(data + "data in process");
Allquestions = JSON.parse(data);
console.log(Allquestions[0].Question + " This is defined");
}
app.get("/", (req, res) => {
res.render("pages/index", { title: "Home"});
});
// app.post("/" , urlencodedParser ,(req , res) => {
// console.log(req.body.topic);
// })
app.get("/questions", urlencodedParser , (req , res) => {
downloadquestions(req.body.topic);
console.log(Allquestions + " this is undefined");
res.render("/pages/quizpage" , {Allquestions})
})
There are a few issues with your code, you have a broken promise chain, client.read( is a promise, and that promise is going nowhere. You either return it, or await it. To be able to await your will need to also mark your route (req, res) as async too.
Your code is a little mixed up, you have Allquestions as a global var, this isn't great for multi-user, as the last topic is going to override this each time.
Also try and avoid swallowing exceptions in utility functions, try and keep your exception handling at the top level, eg. in your case inside your req/res handler.
So with all this in mind, your refactored code could look something like ->
const sheetdb = require('sheetdb-node');
// create a config file
const config = {
address: 'https://sheetdb.io/api/v1/9djmf8ydc7hwy',
};
//sheetdb
// Create new client
const client = sheetdb(config);
async function downloadquestions(topic) {
const data = await client.read({ limit: 2, sheet: topic });
return processQuestions(data);
}
function processQuestions(data) {
return JSON.parse(data);
}
app.get("/", (req, res) => {
res.render("pages/index", { title: "Home"});
});
app.get("/questions", urlencodedParser , async (req , res) => {
try {
const allQuestions = await downloadquestions(req.body.topic);
res.render("/pages/quizpage" , {Allquestions});
} catch (e) {
console.error(e);
res.end('There was an error');
}
})
I want to send back two S3 pre-signed URL's for each key in [user.idKey, user.selfieKey] array in my Express route.
I know that S3 is successfully getting the pre-signed URLS because they will log to the console with the callback console.log(url).
I also tried using "await" in front of the getSignedUrl method but I don't think that works for S3..???
Any idea what I am doing wrong?
Thank you!
router.get(`/api/verification/load`, auth, async (req, res) => {
try {
const user = await User.findOne({ GETS A USER })
let urlArray = []
const keyArray = [user.idKey, user.selfieKey]
for (const key in keyArray) {
s3VerificationBucket.getSignedUrl(
"getObject",
{
Bucket: "app-verification",
Key: key,
Expires: 30,
},
(err, url) => urlArray.push(url) // when console.log(url) it logs urls
)
}
if (urlArray.length === 0) {
console.log("URL ARRAY EMPTY") -> RETURNS "URL ARRAY EMPTY"
}
const idUrl = urlArray[0]
const selfieUrl = urlArray[1]
res.send({ user, idUrl, selfieUrl })
} catch (err) {
res.status(500).send()
}
})
You are sending your response synchronously. You are signing your links asynchronously. So the array is populated AFTER you have already responded.
Instead, use s3VerificationBucket.getSignedUrl(...).promise() to get a promise for each operation.
Use Promise.all(...) to wait on the result of all operations before responding.
Only after you have processed all async work should you res.send(...).
I'm trying to make a simple API that calls another API that will return some information. The thing is, in order to connect to the second API, I need to attach query parameters to it.
So what I've tried to do so far is to use an axios.get in order to fetch the API. If I didn't need to add queries on top of that, then this would be really simple but I'm having a really hard time trying to figure out how to attach queries on top of my request.
I've created an object that pulled the original query from my end and then I used JSON.stringify in order to turn the object I made into a JSON. Then, from my understanding of Axios, you can attach params my separating the URL with a comma.
On line 6, I wasn't sure if variables would carry over but I definitely can't have the tag var turned into the string "tag", so that's why I left it with the curly brackets and the back ticks. If that's wrong, then please correct me as to how to do it properly.
the var tag is the name of the query that I extracted from my end. That tag is what needs to be transferred over to the Axios GET request.
app.get('/api/posts', async (req, res) => {
try {
const url = 'https://myurl.com/blah/blah';
let tag = req.query.tag;
objParam = {
tag: `${tag}`
};
jsonParam = JSON.stringify(objParam);
let response = await axios.get(url, jsonParam);
res.json(response);
} catch (err) {
res.send(err);
}
});
response is SUPPOSED to equal a JSON file that I'm making the request to.
What I'm actually getting is a Error 400, which makes me think that somehow, the URL that Axios is getting along with the params aren't lining up. (Is there a way to check where the Axios request is going to? If I could see what the actual url that axios is firing off too, then it could help me fix my problem)
Ideally, this is the flow that I want to achieve. Something is wrong with it but I'm not quite sure where the error is.
-> I make a request to MY api, using the query "science" for example
-> Through my API, Axios makes a GET request to:
https://myurl.com/blah/blah?tag=science
-> I get a response with the JSON from the GET request
-> my API displays the JSON file
After looking at Axios' README, it looks like the second argument needs the key params. You can try:
app.get('/api/posts', async (req, res, next) => {
try {
const url = 'https://myurl.com/blah/blah';
const options = {
params: { tag: req.query.tag }
};
const response = await axios.get(url, options);
res.json(response.data);
} catch (err) {
// Be sure to call next() if you aren't handling the error.
next(err);
}
});
If the above method does not work, you can look into query-string.
const querystring = require('query-string');
app.get('/api/posts', async (req, res, next) => {
try {
const url = 'https://myurl.com/blah/blah?' +
querystring.stringify({ tag: req.params.tag });
const response = await axios.get(url);
res.json(response.data);
} catch (err) {
next(err);
}
});
Responding to your comment, yes, you can combine multiple Axios responses. For example, if I am expecting an object literal to be my response.data, I can do:
const response1 = await axios.get(url1)
const response2 = await axios.get(url2)
const response3 = await axios.get(url3)
const combined = [
{ ...response1.data },
{ ...response2.data },
{ ...response3.data }
]
so i have this problem i am working on 'following' feature in my application. What's important, i have two models:
Follows and Notifications
When I hit follow button in front-end I run function from follow.client.controller.js which POSTs to API endpoint /api/follows which corresponds to follow.server.controller.js and then update action on Follows model is performed - easy. AFAIK thats how it works (and it works for me).
But in follows.server.controller.js I want also invoke post to API endpoint at /api/notifications which corresponds to notifications.server.controller.js but I can't find a proper way to do that. Any help will be appreciated.
I don't want another call from front-end to add notification because it should be automatic = if user starts following someone, information is saved in both models at once.
You can add middleware in your server route.
app.route('/api/follows')
.post(notification.firstFunction, follows.secondFunction);
And now add 2 methods in your contollers. First makes the call to db and add's some result's data to request object which will be forwarded to second method.
exports.firstFunction= function(req, res, next) {
Notification.doSometing({
}).exec(function(err, result) {
if (err) return next(err);
req.yourValueToPassForward = result
next(); // <-- important
});
};
exports.secondFunction= function(req, res) {
//...
};
Or you can make few database calls in one api method, joining this calls with promises. Example:
var promise = Meetups.find({ tags: 'javascript' }).select('_id').exec();
promise.then(function (meetups) {
var ids = meetups.map(function (m) {
return m._id;
});
return People.find({ meetups: { $in: ids }).exec();
}).then(function (people) {
if (people.length < 10000) {
throw new Error('Too few people!!!');
} else {
throw new Error('Still need more people!!!');
}
}).then(null, function (err) {
assert.ok(err instanceof Error);
});