How to access requested body from another function with async/await? - node.js

Question

sorry for the generic title. I'm pretty new to nodejs as well as the idea of async/await.
So I have an express app, which makes an HTTP get request as a callback function. The callback function gets the body object, and returns it to getBody function. But when I try to assign getBody to a variable, it returns undefined.
Yes I know. The getBody function returns body before body gets filled up with data, but I just don't know how to write a getter method for this body object. So my question is, how can I run the get request and access body object in the global scope at the same time, so all functions depending on body object can run without further problems.
async function getBody (req, res, next) {
let body = await makeRequest(req, res);
return body; // THIS RETURNS UNDEFINED
}
router.get('/', getBody);
function makeRequest (req, res){
let uri;
let options = {
uri: uri,
};
request(options, function (error, response, body) {
if (error){
console.log('error:', error);
} else {
console.log('Success! statusCode:', response && response.statusCode);
let jsonObject = JSON.parse(body);
return jsonObject;
}
});
}
I did my research, but I just could not find a useful resource. Thanks in advance.

Answer 1

await and async should be used with a promise, these kind of method cannot return data. return is used to return a value from a synchronous method.
So you may return a promise from your makeRequest method like this,
async function getBody(req, res, next) {
let body = await makeRequest(req, res);
return body; // NOW BODY IS NOT UNDEFINED, call next() or send response here
}
router.get('/', getBody);
function makeRequest(req, res) {
return new Promise((resolve, reject) => {
let uri;
let options = {
uri: uri,
};
request(options, function (error, response, body) {
if (error) {
console.log('error:', error);
return reject(error);
} else {
console.log('Success! statusCode:', response && response.statusCode);
let jsonObject = JSON.parse(body);
return resolve(jsonObject);
}
});
})
}
FYI,
let body = await makeRequest(req, next)
is equals to
makeRequest(req, next).then(body => { /* YOUR CODE HERE */ })
and if you didn't knew, you have to process the body and send the response, return body won't send the response to the client.

Answer 2

OK, #JanithKasun did a great job of answering your original question fully. This answer is intended to expand on that a little to get a the problem you're having conceptually that isn't explicitly asked in your question.
As I understand your code, you're trying to fetch some data from a third party resource based on information in the request coming to your app's handler. Ideally, you want to separate your code in a way to make it more reusable/maintainable. I note that the code in question doesn't actually use the request or response object at all, but I'm going to assume you would have some kind of parameter to the getBody function that helps you construct the URI it's requesting. So, to that end:
// ./lib/get-body.js
const BASE_URI = 'https://example.com/search?q='
async function getBody (query) {
let body = await makeRequest(query);
return body;
}
function makeRequest(query) {
return new Promise((resolve, reject) => {
let uri = `${BASE_URI}{query}`; // results in something like 'https://example.com/search?q=cats'
let options = {
uri: uri,
};
// Note: removed console statements here to centralize error handling
request(options, function (error, response, body) {
if (error) {
return reject(error);
} else {
let jsonObject = JSON.parse(body);
return resolve(jsonObject);
}
});
})
}
// export the top level function for reuse
module.exports = getBody;
Now, in your routing code:
// ./index.js or wherever
const express = require('express');
const getBody = require('./lib/get-body');
//...whatever other setup...
app.get('/', async (req, res, next) => {
const query = req.query.terms; // or whatever
try {
const body = await getBody(query);
return res.send(body);
} catch (e) {
return next(e); // if you don't do this, process hangs forever on error
}
});
// handle the errors. obviously you can do something smart like
// figure out the error code and send back something other than a 500 if appropriate.
app.use((err, req, res, next) => {
console.error(err);
res.status(500).send('I am Bender; please insert girder.');
});
Hope that helps!