how to make nested REST GET requests in expressjs nodejs

Question

Let's say my route file has the following REST endpoint:

app.get('/userlist', function (req, res) {

    var httpClient = addon.httpClient(req);
    httpClient.get('example.com/users',
        function(error, response, body) {
            if (!error && response.statusCode == 200) {

                var users = JSON.parse(body);
                users.forEach(function(user, index, arr) 
                {
                  //do the 2nd REST GET request here using user.id ???
                }

                res.render('userlist', {
                    content : users
                });
            }
        });
}

The endpoint consumes an RESTful webservice and the result looks like this:

{ users :  [{ id : 12345 },{ id : 23456 },{ id : 34567 }]}

Now i would like to know how / where to do the 2nd. REST GET request ( /userinfo ) to retrieve extra information of the user (based on the user.id from the result of the 1st. request) and update the 1st. result with 2nd.

Regards

Answer 1

Using an httpClient that only supports callbacks, your best bet is to create a function for each step and avoid deeply nested blocks:

function findFirstUser(callback) {
  httpClient.get('example.com/users', (error, response, body) => {
    var firstUserId = JSON.parse(body).users[0]
    getUser(firstUserId, callback)
  })
}


function getUser(id, callback) {
  httpClient.get('example.com/users/' + id, callback)
}

The async library can help you do this as well.

I do not recommend either approach. Instead, use an httpClient that supports Promises , such as axios :

httpClient.get('example.com/users')
  .then(response => JSON.parse(response.body).users[0])
  .then(userId => httpClient.get('example.com/users/' + userId))
  .catch(error => console.error(error))