Express.js Routing error: Can't set headers after they are sent

Question

I'm not really sure why I'm getting this error. It's a simple API built on express.js to be able to add and remove posts. The error occurs when I trigger the delete router. I've read that the error typically happens when there are two callbacks, however, I don't seem to be able find any double callbacks.

    _http_outgoing.js:344     throw new Error('Can\'t set headers after they are sent.');     Error: Can't set headers after they are sent.     at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:344:11)     at ServerResponse.header (/Users/bounty/Projects/_learning/react-express/node_modules/express/lib/response.js:718:10) at ServerResponse.send (/Users/bounty/Projects/_learning/react-express/node_modules/express/lib/response.js:163:12)     at ServerResponse.json (/Users/bounty/Projects/_learning/react-express/node_modules/express/lib/response.js:249:15)     at /Users/bounty/Projects/_learning/react-express/server/routes/posts.js:86:9     at nextTickCallbackWith0Args (node.js:452:9)     at process._tickCallback (node.js:381:13) 

Here is my posts.js router:

module.exports = function(router) {      var Post = require('../models/post.js');      // middleware for the api requests     router.use(function(req, res, next) {         // do logging         console.log('something is happening.');         next(); // make sure we go to our next route and don't stop here     });      // test route to make sure everything is working (accessed at GET http://localhost:8080/api)      router.get('/', function(req, res) {         res.json({ message: 'hooray! welcome to our api!' });        });      // all routes here      // routes that end in /posts     router.route('/posts')          // create a Post (accessed at POST http://localhost:7777/api/posts)         .post(function(req, res) {             var post = new Post();             post.postTitle = req.body.postTitle; // set the post name (comes from request)               // save post and check for errors             post.save(function(err) {                 if (err)                     res.send();                  res.json({ message: 'post created!' });             });         })          // get all Posts (accessed at GET http://localhost:7777/api/posts)         .get(function(req, res) {             Post.find(function(err, posts) {                 if (err)                     res.send();                  res.json(posts);             });         });      // routes that end in /posts for specific id     router.route('/posts/:post_id')          // get the post with that id         .get(function(req, res) {             Post.findById(req.params.post_id, function(err, post) {                 if (err)                     res.send(err);                  res.json(post);             });         })          // update the post with that id         .put(function(req, res) {             Post.findById(req.params.post_id, function(err, post) {                 if (err)                     res.send(err);                  post.postTitle = req.body.postTitle;                  // save the post                 post.save(function(err) {                     if (err)                         res.send(err);                      res.json({ message: 'post updated!' });                 });             });         })          // deletes the post with that id         .delete(function(req, res) {             Post.remove({                 _id: req.params.post_id             }, function(err, post) {                 if (err) {                     res.send(err);                 }                 res.json({ message: 'post deleted!' });             });         }); } 

Answer 1

You need to add the 'return' so that you don't reply twice.

// save post and check for errors post.save(function(err) {     if (err) {         return res.send();     }     res.json({ message: 'post created!' }); });