how to get data outside request - node.js

Question

I have a scenario where i need to take response (body) of request method outside request. How can i do it?
request.post({
url: 'http://localhost/api/messages',
form: { key: message }
}, function (err, httpResponse, body) {
tmsg = body;
})
console.log(tmsg);
I need this tmsg outside for next processing, Actual scenario is as below.
app.post('/incomemsg', function (req, res) {
var mediaCount = req.body.NumMedia;
if (mediaCount == 0) {
//var twiml = getResponse(message);
var twiml = new MessagingResponse();
request.post({
url: 'http://localhost:3978/api/messages',
form: { key: message }
}, function (err, httpResponse, body) {
tmsg = body;
})
console.log(tmsg);
}else {
//dosomething which outputs tmsg
}
res.writeHead(200, { 'Content-Type': 'text/xml' });
res.end(tmsg.toString());
});

Answer 1

The problem is you are trying to assign value to a global variable in request.post's callback() which is only called after request.post is executed by Asynchronous logic(API calls are all async), so a better way would be to promisify request.post and await the request.post to make it seem synchronous.
const requestPromisified = requestObject =>
new Promise((resolve, reject) => {
request.post(requestObject, function(err, httpResponse, body) {
if (err) {
reject(err);
}
resolve(body);
});
});
const body = await requestPromisified({
method: "POST",
url: "http://localhost/api/messages",
form: { key: message }
});

Answer 2

You only can do something with tmsg when you made the request so you need to rearrange your code like this:
app.post('/incomemsg', function (req, res) {
var mediaCount = req.body.NumMedia;
var twiml = new MessagingResponse();
request.post({
url: 'http://localhost:3978/api/messages',
form: { key: message }
}, function (err, httpResponse, body) {
tmsg = body;
console.log(tmsg);
if (mediaCount === 0) {
//do something with tmsg
} else {
//do something else with tmsg
}
res.writeHead(200, { 'Content-Type': 'text/xml' });
res.end(tmsg.toString());
});
});
Otherwise tmsg will be null because there was no request made to fill that variable.