CODEWITHSUNDEEP
javascriptnode.jsexpress
Yh1234
Yh1234

Reputation: 151

Node throw new Error('Can\'t set headers after they are sent.')

I am having the above problem with one of my node calls. To my knowledge this error shows if you res.send gets called more than once. Looking at the code it should only send res once so I am not sure what is wrong here.

It throws the error when I insert

var express = require('express');
var bodyParser = require('body-parser');
var session = require('express-session');
var cors = require('cors');
var massive = require('massive');
var config = require('./config');
var app = express();
app.use(bodyParser.json());
app.use(cors());

var db = massive.connect({connectionString: config.connectionString}, function(err, localdb){
    db = localdb;
    app.set('db', db);
});
app.post('/api/login', function(req, res, next) {
    db.get_users(function(err, users) {
        if(err) res.status(500).json(err);
        else {
            for(var i = 0; i < users.length; i++) {
                if(req.body.email == users[i].email && req.body.password == users[i].password) {
                    console.log("matched");
                    var currentUser = users[i];
                    res.send({
                        msg: 'passed',
                        user: currentUser
                    });
                }
                else { res.send("Username or Password is wrong"); }
            }
        }
    })
})
app.listen(3000, function() {
    console.log("I am listening");
});

Upvotes: 0

Views: 32

Answers (1)

jfriend00
jfriend00

Reputation: 707148

You are doing res.send() inside a for loop. That means you're calling it multiple times. The error you see is caused when you try to send more than one response to the same request. You can't do that.

I don't know exactly what you're trying to accomplish, but you can either accumulate results in the for loop and send one response after the for loop or you can break or return out of the for loop as soon as you send a response. The point is that you can only send one response.

Upvotes: 1

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