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JavaScript Build a Simple Dynamic Site with Node.js Handling Routes in Node.js Populating User Information

Posted by David Drysdale
David Drysdale
10,815 Points

Server crashing after successfully displaying JSON data

I'm having a peculiar issue.

Everything works fine for the home route and for the error route, but when I write in a valid username, I get the correct data but the server then crashes with the following error:

Server running at port 3000.                                                                  
events.js:141                                                                                 
      throw er; // Unhandled 'error' event                                                    
      ^                                                                                       

Error: write after end                                                                        
    at ServerResponse.OutgoingMessage.write (_http_outgoing.js:413:15)                        
    at Profile.<anonymous> (/home/treehouse/workspace/router.js:39:16)                        
    at emitOne (events.js:77:13)                                                              
    at Profile.emit (events.js:169:7)                                                         
    at IncomingMessage.<anonymous> (/home/treehouse/workspace/profile.js:38:36)               
    at emitNone (events.js:72:20)                                                             
    at IncomingMessage.emit (events.js:166:7)                                                 
    at endReadableNT (_stream_readable.js:905:12)                                             
    at nextTickCallbackWith2Args (node.js:441:9)                                              
    at process._tickCallback (node.js:355:17)

Here is what's in my router.js file:

var Profile = require("./profile.js");

// Handle HTTPS route GET / and POST / i.e. Home
function home(request, response) {
  // if url == "/" && GET
  if(request.url === "/") {
    // Show the search field
    response.writeHead(200, {'Content-Type': 'text/plain'});
    response.write("Header\n");
    response.write("Search\n");
    response.end('Footer\n');
  }
  // if url == "/" && POST
    // redirect to /:username
}

// Handle HTTP route GET /:username i.e. /chalkers
function user(request, response) {
  // if url == "/..."
  var username = request.url.replace("/", "");
  if(username.length > 0) {
    response.writeHead(200, {'Content-Type': 'text/plain'});
    response.write("Header\n");

    // get json from Treehouse
    var studentProfile = new Profile(username);
    // on "end"
    studentProfile.on("end", function(profileJSON) {
      // show profile

      // Store the values we need
      var values = {
        avatarUrl: profileJSON.gravatar_url,
        username: profileJSON.profile_name,
        badges: profileJSON.badges.length,
        javascriptPoints:profileJSON.points.JavaScript
      }
      // Simple response
      response.write(values.username + ' has ' + values.badges + ' badges.\n');
      response.end('Footer\n');
    });

    // on "error"
    studentProfile.on('error', function(error) {
      // show error
      response.write(error.message + '\n');
      response.end('Footer\n');
    });

  }
}

module.exports.home = home;
module.exports.user = user;

Any ideas? I was wondering at first that I was having a problem because the data displays on end, and then I have the response.end line, but that's the way the error works, too, and I don't have a problem with that.

EDIT: Here's a snapshot of my workspace: https://w.trhou.se/srfspy68i9

Ryan Chatterton
Ryan Chatterton
5,914 Points
Ryan Chatterton
Ryan Chatterton
5,914 Points

Hi David,

in your code:

var username = request.url.replace("/", "");
  if(username.length > 0) {
    response.writeHead(200, {'Content-Type': 'text/plain'});
    response.write("Header\n");

    // get json from Treehouse
    var studentProfile = new Profile(username);
    // on "end"
    studentProfile.on("end", function(profileJSON) {
      // show profile

      // Store the values we need
      var values = {
        avatarUrl: profileJSON.gravatar_url,
        username: profileJSON.profile_name,
        badges: profileJSON.badges.length,
        javascriptPoints:profileJSON.points.JavaScript
      }
      // Simple response
      response.write(values.username + ' has ' + values.badges + ' badges.\n');
      response.end('Footer\n');
    });

is executed synchronously, but each call does asynchronous calls to external ressources before calling response.write. So response.end is getting called to early. 

 // store values which we need
      var values = {
        avatarUrl: profileJSON.gravatar_url,
        username: profileJSON.profile_name,
        badges: profileJSON.badges.length,
        javascriptPoints: profileJSON.points.JavaScript
      }
      // simple repsonse
      renderer.view("profile", values, response);
      renderer.view("footer", {}, response);
      response.end();

  });

    // on "error"
    studentProfile.on("error", function(error) {
      // show error
      renderer.view("error", {errorMessage: error.message }, response);
      renderer.view("search", {}, response);
      renderer.view("footer", {}, response);
      response.end();
    });

4 Answers

Ryan Chatterton
Ryan Chatterton
5,914 Points
Ryan Chatterton
Ryan Chatterton
5,914 Points

If I remember when I did this, it has a lot of bugs mainly because its older. here is the project all finished (snap shot of mine). https://w.trhou.se/f3cwzn7q65

You will run into this as well https://teamtreehouse.com/community/cant-display-username-receiving-error

Rune Rapley-Møller
Rune Rapley-Møller
Courses Plus Student 24,411 Points
Rune Rapley-Møller
Rune Rapley-Møller
Courses Plus Student 24,411 Points

Hi Ryan, could you repost your workspace snapshot again (it's not found 404).?

I keep getting the following error: error connect econnrefused ?

any advice towards the right direction is much apreciated.

Thx

David Drysdale
David Drysdale
10,815 Points
David Drysdale
David Drysdale
10,815 Points

Thanks, Ryan Chatterton—good to know it isn't just me. It is a bit frustrating that the lesson includes such buggy code, though. I spent a lot of time trying to debug it, while also trying to figure out how to apply it to a project of my own. I hope they update this course soon.

Abirbhav Goswami
Abirbhav Goswami
15,450 Points
Abirbhav Goswami
Abirbhav Goswami
15,450 Points 
// get json from Treehouse
    var studentProfile = new Profile(username); 
    // on "end"
    studentProfile.on("end", function(profileJSON) { // <-- Problem lies on this line
      // show profile

Since the profile is shown on request end, you cannot write anything after the first successful call.

David Drysdale
David Drysdale
10,815 Points
David Drysdale
David Drysdale
10,815 Points

Thanks, Ryan Chatterton . I'm still confused, though, because I don't think my code's any different from Andrew Chalkley's code at this point, and his seems to work without getting that error. Is there some way to fix this, or is it a fault in the lesson? (And if so, will it be fixed, I wonder.)

Tyler Taylor
Tyler Taylor
17,939 Points
Tyler Taylor
Tyler Taylor
17,939 Points

Ryan's answer skipped a few lessons ahead. So I just kept going until I got to that part, now my server doesn't crash. My code was exactly the same as Andrew's, and I was experiencing the same issue as you. I'm a little annoyed with the quality of these lessons. It's as if they had to record it in one shot, with no editing.