是否将req.query ['name']的值保存到Node.jS中的变量？

Question

I am coding a login system in node.js, I am trying to do this:

var auth = req.query['name']

to which I would then compare auth with the result from the database query, but when ever I try and load the page with /?name=foo I get this error:

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

my current code is:

var express = require('express');
var app = express();

app.get('/', function(req, res){
    res.send('hello! every thing is working!');
    var auth = req.query['name']
    if (auth === "ozzie"){// I will obviously change this.
        res.send('Hello! Your details have been authenticated')
    }
    else
    {
        res.send('Sorry! That did not work! please try again! ')
    }
});


app.listen(8888, '127.0.0.1'); 
console.log('running on, local Ip + 8888');

Answer 1

The problem is that you're attempting to send two responses to the same request, the first time with

res.send('hello! every thing is working!');

and the second time is inside the if or else block. Remove the first one and it should work fine or concatenate the output and have just one res.send() that is passed the concatenated output.

Answer 2

You are sending a response at the beginning of your callback:

app.get('/', function(req, res){
     res.send('hello! every thing is working!'); // here

Then, calling the same thing in a conditional if - else block once more. Since calling the send() method sets headers, you end up doing the same twice.

Remove the first one and you'll be OK.

Note: For debugging purposes you could resort to using console.log and view the debug info on the console where you ran your application's main file.