Return of Request (Node.js)

Question

I’m trying to consume an API with request, but I’d like to know how to assign the return to a variable. Here’s my code:

var response
function getWeather() {
    request(url, function (error, response, body) {
        console.log(body)
        response = body
    })
}
console.log(response)

The console.log(body) returns the string value, but the console.log(Response) returns Undefined. I would like the Answer variable to capture the body content for me to manipulate. How can I do this?

Answer 1

Your "problem" consists of the fact that this request made by the module is asynchronous i.e.: the request will be made and subsequently you will get a reply, either the body of the request or an error that occurred in the request.

You are declaring a variable without a content (response) hoping to assign a value to it when the answer comes though, is accessing (using) this variable before it happens (console.log) ... will always be undefined

You must use a callback to work on this value, example:

const request = require("request");

function getWeather(callback) {
    request(url, function (error, response, body) {
        callback(body)
    })
}

getWeather(function(responseBody) {
    console.log(responseBody)
})

By default this module does not work with Promise() but as described by the module itself you can use the adjacent packages if you want to work on "Promises" see links of adjacent packages:

https://www.npmjs.com/package/request#Promises-asyncawait

If you don’t want to use extra packages know that you can do this natively using the native module utils and "promising" the request:

const util = require('util')
const request = require("request");

const requestPromise = util.promisify(request);

function getWeather(url) {
    return requestPromise(url).then(response => {
        if ( response.statusCode === 200 ) {
            return response.body
        }
        return Promise.reject(response.statusCode)
    })
}    

getWeather('https://www.google.com').then(body => {
    console.log(body)
}).catch(e => console.log(e))

Since not all possible status codes are an error in the request you should treat them as you really want them, the above example will only return the body of the request if the status is equal to 200 and reject all others.

Promise() by nature are "asynchronous" functions but you can use await to work on a "synchronous" behavior as long as it is within a function async:

const util = require('util')
const request = require("request");
const requestPromise = util.promisify(request);    


async function done() {
    let response = await requestPromise('https://www.google.com')
    console.log(response.body)
}    

done()

In the above example there is no guarantee that the answer will have a property "body" and cannot do any treatment in case of error/failure other than that all the code will "wait" for the order to complete and a server may take too long to respond.

A "better" approach would be to address possible gaps in the request in a block .catch():

const util = require('util')
const request = require("request");
const requestPromise = util.promisify(request);


async function done() {
    async function getWeather(url) {
        return requestPromise(url).then(response => {
            if ( response.statusCode === 200 ) {
                return response.body
            }
            return Promise.reject(response.statusCode)
        }).catch(err => {
            return err
        })
    }

    console.log(await getWeather('https://www.google.com'))
}

done()

---

reading:

Mozilla Docs: async/await

Answer 2

The ideal is that you give a Return in the Weather that consumed by the API in the getWeather method and so use the getWeather method where you want.

For example:

async function getWeather() {
    return request(url, function (error, response, body) {
        if (response.status === 200)
           return body

        return false
    })
}

Note: I have not tested the code and I do not know if request solves a Promise, if it is may not work. But it is just to give you a notion.

Later you just call the function to consume the API and already get the value where you want.

const weather = await getWeather()

Understood the concept?