NodeJS HTTP Requests Promises and Storing Results in Variables - node.js

Question

I'm building a front-end application that makes HTTP requests to 2 separate API's.
http://greetings_api:3000/getGreeting
data {'language': 'es'}
Response: 'Hola'
http://users_api:3000/getUser
data {'userid': 1}
Response: 'Jose Smith'
I have a single route that makes a request to these API's and then returns those responses:
var http = require('http');
var request = require('request-promise');
var greetingOptions = {
uri: 'http://greetings_api:3000/getGreeting',
hostname: 'greetings_api',
method: 'POST',
headers: {
'Content-Type': 'application/json',
'language': 'es'
}
};
var greeting = {
getGreeting: function() {
return request(greetingOptions);
}
}
function myGreeting() {
return greeting.getGreeting();
};
var userOptions = {
uri: 'http://users_api:3000/getUser',
hostname: 'users_api',
method: 'POST',
headers: {
'Content-Type': 'application/json',
'id': 1
}
};
var user = {
getUser: function() {
return request(userOptions);
}
}
function myUser() {
return user.getUser();
};
function getWelcome(req, res) {
// How do you store this....
myUser().then(function(result) {
console.log('result')
return result;
})
// ...and this...
myGreeting().then(function(result) {
console.log('Greet ' + result);
return result;
});
/// ...and then send them with this?
res.send(greeting + ' ' + user);
}
module.exports = { getWelcome };
So with the current code I get the correct output in the console. The problem is that I need to be able to send the response from the route with the combination of both API responses. What is the simplest way to accomplish this?

Answer 1

You are sending the response before the promises resolving.
with async/await we can write asynchronous code that looks and behaves like synchronous.
async function getWelcome(req, res) {
// we can wrap our operation in a try/catch block to handle
// both asynchronous and synchronous errors
try {
// with the await keyword we can wait for all promises to resolve
// before we continue with our code
/* if one of the promises inside Promise.all rejects we move to the catch block */
const [user, greeting] = await Promise.all([
myUser(),
myGreeting()
]);
// send the response if no errors
res.send(greeting + ' ' + user);
catch(e) {
res.status(404).send();
}
}

Answer 2

You need to make 2 parallel requests and send response after completing both. Here Promise.all function can help you.
Promise.all([myUser(), myGreeting()]).then(function(result) {
// result[0] - user
// result[1] - greeting
res.send(result[0] + ' ' + result[1]);
});