Cannot access variable inside request function JS

Question

I have a function which should return an access token. Inside a function there is a request, which gives me the token. But I can not acces it in the main function.

Here is my code from inside a function:

 var accessToken = 'test1'; request.post(authOptions, function(error, response, body) { accessToken = body.access_token; console.log('test2 ' + accessToken); }); console.log('test3 ' + accessToken);

It gives the following result:

test3 test1

(node:14744) ExperimentalWarning: stream/web is an experimental feature. This feature could change at any time

(Use node --trace-warnings ... to show where the warning was created)

test2 BQDzZHO1Eg99...

The accessToken gets the value inside the request as seen in test2, but when I retrieve it after the function, it hasn't got it yet. How can I use it after? eg. in function retrieve

Answer 1

When you do request.post your code has to wait for a response from the server you are posting to. This response is handled in your function(error, response, body) function (passed in as the 2nd argument to request.post . But in the meantime the rest of your function will continue to be executed. I've added comments to try and explain this futher:

var accessToken = 'test1'; // First line of your code is executed first

// Now we execute request.post
request.post(authOptions, function(error, response, body) {
  // This is only executed whenever the response is received.  It may be many milliseconds later
  accessToken = body.access_token;    
  console.log('test2 ' + accessToken);
});

// This is executed immediately after the `request.post`.  Therefore accessToken will still be 'test1'.
console.log('test3 ' + accessToken);

Instead you can return a Promise or use callbacks to get the accessToken from this function. Here is a basic callback function:

function getAccessToken(callback) {
  request.post(authOptions, function(error, response, body) {
    callback(body.access_token);
  });
}

getAccessToken(function(myToken) {
  // Here is your token.
});