Get from URL data and convert to JSON array

Question

I have this function

function getJsonObjectFromURL(url, onData) {
  let chunks = [];
  return require('https').get(url, res => {
    res.setEncoding('utf8')
      .on('data', (chunk) => {
        chunks.push(chunk);
      })
      .on('end', () => {
        onData(JSON.parse(chunks.join('')));
      });
  }).on('error', function(e) {
    console.log("Got an error: ", e);
  });
}

Also I have this script that converts url's data to json array.

url = https://pu.vk.com/c824502/upload.php?act=do_add&mid=213468131&aid=-14&gid=156603484&hash=7ab9a7e723425f4a6ca08709cbd5ebd0&rhash=ba8f0ec6580a6eafce38349b12ed3789&swfupload=1&api=1&wallphoto=1
    getJsonObjectFromURL(url, data => {
      console.log(data.server, data.photo, data.hash);
    });

It goes well when console.log. But when I want to make from this script variable, it gives me huge collection

var xx = getJsonObjectFromURL(url, data => {
  return data.server;
});
console.log(xx);

HugoTeixeira · Accepted Answer · 2018-07-21 17:01:04Z

1

Your function getJsonObjectFromURL() doesn't return the object returned by the URL. It returns the object responsible for the https request code, which is something you don't want.

I see that you are using ES6, so the best solution for you is to probably create an async function that returns a promise, which will give you great flexibility. Here is an improved version of your code:

const https = require('https');

async function getJsonObjectFromURL(url) {
    return new Promise((resolve, reject) => {
        const chunks = [];
        try {
            https.get(url, res => {
                res.setEncoding('utf8')
                .on('data', (chunk) => {
                    chunks.push(chunk);
                })
                .on('end', () => {
                    resolve(JSON.parse(chunks.join('')));
                });
            }).on('error', e => reject(e));
        } catch (err) {
            reject(err);
        }
    });
};

This code allows you to retrieve the remote contents of the HTTPS url synchronously or asynchronously.

Asynchronous Call

As you have already done in your code, you can use a lambda callback that handles the response when it is ready.

const url = 'https://pu.vk.com/c824502/upload.php?act=do_add&mid=213468131&aid=-14&gid=156603484&hash=7ab9a7e723425f4a6ca08709cbd5ebd0&rhash=ba8f0ec6580a6eafce38349b12ed3789&swfupload=1&api=1&wallphoto=1';

// here we use a lambda callback that handles the response
getJsonObjectFromURL(url)
    .then(data => {
        console.log(data.server, data.photo, data.hash);
    })
    .catch(err => console.error(err));

Synchronous Call

The synchronous call forces the function to wait for the result. This is how you can do it:

async function getSync() {
    try {
        // wait for the result
        const data = await getJsonObjectFromURL(url);
        console.log(data.server);
    } catch(err) {
        console.error(err);
    } 
}   
getSync();

Please note that we can only use the await keyword when we are inside an async function. This is why I had to wrap the synchronous call with a function.

edited Jul 21, 2018 at 17:01

answered Jul 21, 2018 at 2:06

HugoTeixeira

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2 Comments

Jengas Over a year ago

But there is console.log, but I wanted to get result to variable to use in other function. How can I do then?

HugoTeixeira Over a year ago

In the Synchronous Call example, the "data" variable receives the result. You can pass that variable to other functions.

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