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Unable to get the variable value outside the http call

I have written below code to get the response data chunk in the variable called outBody, but it is showing undefined. Any suggestions please?
var options = {
host: 'jsonplaceholder.typicode.com',
port: 80,
path: '/todos/1'
};
var outBody;
http.get(options, function(res) {
console.log("Got response: " + res.statusCode);
res.on("data", function(chunk) {
outBody = chunk;
});
}).on('error', function(e) {
console.log("Got error: " + e.message);
});
console.log(outBody);
I actually want to use the variable outBody outside the http request. How can I use it?

Your code is showing undefined, because your code is a asyncronous code and you are logging data synchronously.
A simple fix is that put your console.log inside the data event listener like this
res.on("data", function(chunk) {
outBody = chunk;
console.log(outBody);
});
and if you want to use the outBody variable outside the http.get then you either has to use promises or a callback function inside another event listener called end , which fires when the response is completed.
Like this
using CallBack :-
//Your code
res.on("data", chunk => {
outBody += chuck
});
res.on("end", () => {
// this event fires when the response body is completely loaded ...
myFunction(outBody); // pass the respone body to your callback function
}
// remaing code
Wanna learn how to deal with this problem again, then learn about async / await and promises on internet
OR
Using promises / async await :-
const options = {...}
var outBody = "";
const req = new Promise( (resolve, reject) => {
http.get(options, res => {
res.on("data", chunk => { outBody += chunk });
res.on("end", () => resolve(outBody));
res.on("error", console.error);
});
});
req.then( data => {
myFunction(data);
})
.catch(err => console.error(err));
// or u can try async / await
(async function (){
const data = await req;
})();
Note : You had done a mistake i.e., inside the data event listener you overwrite the outBody with the new chunk. It is a mistake because the http class loads the response in chuck which means parts. It means you are losing data , I also fixed it by adding += in place of outBody = chunk, it simply appends the new part the older part which gives you the complete response body...
Still confused about the promises and async / await , then them here

The http request is asynchronous, the reason why console.log is logging undefined is because you log the result of the request before the request is done, only after the request is done outbody gets the value of chunk. In order to access the outbody value you should write the console.log inside the callback block which is called right after the data is returned from the request like this:
http.get(options, function(res) {
console.log("Got response: " + res.statusCode);
res.on("data", function(chunk) {
outBody = chunk;
console.log(outbody)
});
res.on("error",e=>{
console.log("Got error: " + e.message);
})
})

Passing data from Nodejs http get request

I am trying to pass data out of my get request from resp.on function. I want to use 'var url' to make a separate get request from which I will parse data again. I am able to console.log variables from inside the function but not return (or access from outside). This seems to be a scoping or async issue.
const https = require('https');
https.get('https://collectionapi.metmuseum.org/public/collection/v1/objects', (resp) => {
let data = '';
// A chunk of data has been recieved.
resp.on('data', (chunk) => {
data += chunk;
});
// The whole response has been received. Print out the result.
resp.on('end', () => {
var json_data = JSON.parse(data);
var total = json_data.total
var random_objectID = Math.floor(Math.random()*total)
var url = 'https://collectionapi.metmuseum.org/public/collection/v1/objects/' + random_objectID
console.log(url);
});
}).on("error", (err) => {
console.log("Error: " + err.message);
})
//'url' becomes unknown here. I want to pass it to another get request.

It's both an async and a scope issue!
If you declare var url; in the outermost scope you'll be able to set it inside that callback as intended, but since that's happening asynchronously you won't be able to use the value outside the scope unless you are checking after the callback completes.
Alternatively, you could wrap the whole thing in a promise, e.g.
const https = require('https');
new Promise((resolve,reject)=>{
let targetUrl = 'https://collectionapi.metmuseum.org/public/collection/v1/objects';
https.get(targetUrl,resp=>{
// ...
resp.on('end', () => {
// ...
resolve(url);
});
});
}).then(url=>{
// do stuff with that URL
});
If your goal is to automate fetching data from web resources, I'd recommend checking out the request module, which also has a promisified variant.

Odoo javascript change value

I Use odoo 10 and want to change pivot_view.js
I'm really confused with this code. I can't change the value.
Can you explain me about the right code ?
This is my code :
var value = false;
new Model('lhp.master').call('getValues', ['date', 'idx']).then(
function (result) { value = result[0]; }
);
console.log('value =',value);
Thank you for your help.

I think the problem is with how javascript promises work!
The order of the execution of the code is a s follows:
var value = flase;
calling the server method getValue by sending an http request;
console.log('value =',value); // which will print "value =fasle" on the console
after the http request earlier in step 2 is finished and a response is retrieved from the server. The callback function will be called with the result:
function (result) { value = result[0]; }
So, make sure to write the console.log part inside the callback method, like this:
function (result) {
value = result[0];
console.log('value =', value);
}

Callback runs first? - learnyounode juggling

Can someone help me understand why my solution does not work? It seems like the callback function is running before the juggle function is finished.
My code works fine if I remove the comments. It's just that I don't understand why the log function does not get called after the juggle function is finished. That is how callbacks are supposed to work right?
Thanks in advance :)
var http = require('http')
links = process.argv.slice(2)
var contents = []
//var cbacks = 0
function juggle(callback) {
links.forEach(function(link, i, links) {
http.get(link, function(response) {
response.setEncoding("utf8")
var str = ""
response.on("data", function(data) {
str = str.concat(data)
})
response.on("end", function(){
contents[i] = str
//cbacks++
//if(cbacks === 3) {
// callback()
//}
})
})
})
callback()
}
function log() {
contents.forEach(function(content, i, contents) {
console.log(contents[i])
})
}
juggle(log)

http.get is asynchronous. forEach is executed against your links which calls http.get, which registers a connection to be processed. It doesn't actually complete the connection/request.
if you need to execute the callback when all the forEach functions complete you could use a library like async to accomplish it.
async supports a forEach method. Using async, the first param to forEach would take an additional callback function which should be called to denote item processing has been finished. You could place that callback in the response.on('end') callback. When all of those callbacks have been called, or when an error has occurred async.forEach will execute the onComplete callback you provide to it as the 3rd parameter, accomplishing your goal.

So you have global scope which is what I would use to actually juggle the requests.
When each link gets registered to an EventEmitter, you can store it inside of a map.
var link_map = {};
var request_counter = 0;
links.forEach( function (link, index) {
link_map[link] = '';
...
then in your requests you can append data from a specific request
response.on('data', function (chunk) {
link_map[link] += chunk.toString();
...
and finally at each end, check if all requests have finished
response.on('end', function () {
request_counter += 1;
if ( links.length === request_counter ) {
// do your logging stuff here and you have all
// the data that you need inside link_map
...
the link variable inside of the anonymous function declared in the forEach is stored for that closure. So each time that the 'data' event is emitted, the link variable is going to refer to the request for a specific link that was registered to the callback. That is why I chose to use a map data structure and map specific data to each link which we are using as a key.
EventEmitters and callbacks can get kind of harry if you are unfamiliar with them. Keep practicing though and it will eventually become easier.
And using an array as you did is not incorrect or anything, I just prefer to use Objects with key => value pairs when I can.
RUN THIS CODE on your machine to see it in action.
const http = require('http');
var links = [
'http://www.google.com',
'http://www.example.com',
'http://www.yahoo.com'
];
var link_map = {};
var request_counter = 0;
links.forEach( function (link, index) {
link_map[link] = '';
http.get(link, function(response) {
response.on('data', function (chunk) {
link_map[link] += chunk.toString();
});
response.on('end', function () {
request_counter += 1;
if ( links.length === request_counter ) {
links.forEach( function(link) {
require('fs').writeFileSync(link.split('//')[1],link_map[link]);
});
}
});
});
});
You can see an output of files from links in the parent directory.

You didn't wait for http response and call callback function immediately. At this point of code contents array is empty.

Callback on node.js http REST call issue

Have a following node.js call to http get REST API. When I run it, it returns the JSON result. However, I am trying to get the result to console.log on var r after assigning the result. Why do I always get undefined? Looks like I am messing up the javascript scope. Any help is appreciated.
var http = require('http'),
oex_appId = 'myappId',
_hostname = 'openexchangerates.org',
_path = '/api/latest.json?app_id=' + oex_appId;
var r;
function getRates(cb) {
var options = {
hostname: _hostname,
path: _path,
method: 'GET'
};
var responseCallback = function(response) {
var latestRates = '';
var parseCurrencies = function(rates) {
var currencies = JSON.parse(rates);
currencies.rates['USD'] = 1;
return currencies.rates;
};
response.setEncoding('utf8');
response.on('data', function(chunk) {
latestRates += chunk;
}).on('error', function(err) {
throw new Error(err);
}).on('end', function() {
cb(parseCurrencies(latestRates));
});
};
var req = http.request(options, responseCallback);
req.on('error', function(e) {
throw e;
});
req.end();
};
var d = function(data) {
console.log(data["INR"]);
currencies["INR"].amount = data["INR"];
r = data;
};
getRates(d);
console.log(r);

Why do I always get undefined?
Your problem is not an scope issue but a misunderstanding of async execution. In this code you are printing the value of r before it is assigned.
The execution of your code is as follow:
getRates() is called
console.log(r) is called (hence you get undefined)
When the request executed in getRates finishes your callback is THEN executed. This is when you are assigning a value to r but by then is too late since you already printed it.
In general, you cannot expect the next line to have a value that will be assigned via an async callback. Instead you should reference the value inside the callback. In your case you should move the console.log(r) inside your callback function d.