Proper pattern to set a variable via Node async call

Question

Proper pattern to set a variable via Node async call

I'm doing an HTTP post, which returns single 10-15 character string. I want to assign this value to a temporary variable and use it while building up another larger string which will contain said 10-15 digit character string.

I've gotten this to work by making the temp variable ("ticket") global, which I don't like:

var ticket; // Global. Lame.


...stuff happens

getTicket("someUser", function(err) {
    if(err) 
       {console.log("problem");}
    else
       {console.log(ticket);}   
});

...other stuff happens

// Helper functions down here....

var getTicket = function (userName, callback) {

  var user = userName;   
  request.post( 
        {
            url: 'http://somewhere',
            form: { 'username': user }
        },
        function(err, response, body) {
            if(err) {
                callback(err);
                return;
            } else {
                ticket = body;        
            }
            callback(null);
        });
}

Can someone point me to the proper pattern to return the variable ticket in the POST's callback (or the body variable, whatever) ala:

_ticket = getTicket("someuser")

Thanks much.

javascript
node.js
asynchronous

Answer 1

You'd pass ticket as a parameter into your callback:

getTicket("someUser", function(err, ticket) {
    if(err) 
       {console.log("problem");}
    else
       {console.log(ticket);}   
});

function getTicket (userName, callback) {

    var user = userName;   
    request.post( 
        {
            url: 'http://somewhere',
            form: { 'username': user }
        },
        function(err, response, body) {
            if(err) {
                callback(err);
                return;
            }
            callback(null, body); // body contains the ticket
        });
}

request.post is async, so there isn't a pattern that will get you something like:

_ticket = getTicket("someuser")