Can't set headers after they are sent error. Node JS

Question

i am new to JavaScript and Node JS. i have the following code:

app.post('/sendSensorsUserIds', function (req, res) {
  var myBody= req.body;
  var sensors= myBody.Sensors;
  var ids= myBody.ids;
  DButils.getSensorsUserIds(connection, ids , sensors , function(ids){
    return res.sendStatus(ids);
  });  
  res.end();
});

I always get the following error:

C:\Users\Daniel\Server\node_modules\mysql\lib\protocol\Parser.js:82
        throw err;
        ^

Error: Can't set headers after they are sent.

some one has any idea what is the problem?

Possible duplicate of [Node.js Error: Can't set headers after they are sent](http://stackoverflow.com/questions/7042340/node-js-error-cant-set-headers-after-they-are-sent) — Ben Fortune, Dec 21 '15 at 13:11
You don't need `res,end` at the bottom. And probably you meant `res.json(ids)` in your db query handler — Vsevolod Goloviznin, Dec 21 '15 at 13:11
@danieltheman if you've read the docs and the concepts of node.js in general, you wouldn't be asking the question in the first place — Vsevolod Goloviznin, Dec 21 '15 at 13:20
well this is an help platform, if you dont want to help, you dont have to... — Dan The Man, Dec 21 '15 at 13:26
@danieltheman how can you learn if you can't read the docs of the tools you use? We can't help you with every problem that you bump into (which has already been solved 100500 times and you're just too lazy to google for it) — Vsevolod Goloviznin, Dec 21 '15 at 15:16

score 0 · Answer 1 · answered Dec 21 '15 at 15:08

res.end() is getting called before the callback in DButils.getSensorsUserIds. I suggest ,

app.post('/sendSensorsUserIds', function (req, res) {
  var myBody= req.body;
  var sensors= myBody.Sensors;
  var ids= myBody.ids;
  DButils.getSensorsUserIds(connection, ids , sensors , function(ids){
    return res.status(ids).end();
  });  

});

score -1 · Answer 2 · answered Dec 21 '15 at 13:14

It is because you are sending the status after res.send() is executed. Try removing res.send();

app.post('/sendSensorsUserIds', function (req, res) {
  var myBody= req.body;
  var sensors= myBody.Sensors;
  var ids= myBody.ids;
  DButils.getSensorsUserIds(connection, ids , sensors , function(ids){
    return res.sendStatus(ids);
      });  

});

Can't set headers after they are sent error. Node JS

2 Answers2