use for loop in node js?

Question

i am using for loop to retrieve the data from mongodb and display it on the browser but the problem it it iterates only for the first time and stops. So i get only the first entry as the output. Whereas it gives the correct output in the console log. Please help?

var movieSchema1 = new mongoose.Schema({
  name:String,
  address:String,
  location:String
});

var user=mongoose.model('movie', movieSchema1, 'movie');

for (var i = 0; i < user.length; i++) {
  res.json("iteration " + i);
  res.json('name:' + user[i].name + user[i].address);
}

Where is user defined/initialized? Not shown in your code snippet above. — Brian Driscoll, Sep 10 '17 at 19:41
res.json only wants to be called once. Build up your result first, maybe use an array for this. — Keith, Sep 10 '17 at 19:44
`res.json()` sends an object and then ENDs the response. You cannot ever call it more than once on the same response object and expect it to work. Build your object in the loop and then `res.json()` it at the end. — jfriend00, Sep 11 '17 at 00:34

score 2 · Answer 1 · answered Sep 10 '17 at 19:51

2

As others have said, build up an object for your response, then res.json() it. Because you're trying to send an array, just use .map() to transform each one:

//turn the array of users into the objects we want to send
const responseData = user.map( (movie, i) => {
   return {
      iteration: i,
      name: movie.name + ' ' + movie.address
   };
});

//this converts the array to a string for you
res.json( responseData );

answered Sep 10 '17 at 19:51

Duncan Thacker

5,073
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Yes this works,but it gives the output in json format,i simply want to display the key and value without json format ?what changes need to be done – Radhika Obhan Sep 10 '17 at 20:04
nice answer! @DuncanThacker – Ahmed Can Unbay Sep 10 '17 at 20:12
You need to get each index and the value then write it to the response @RadhikaObhan check my update – Ahmed Can Unbay Sep 10 '17 at 20:13
1

If you don't want JSON, why are you using res.json()? – Duncan Thacker Sep 10 '17 at 20:26
@DuncanThacker what alternate can I use to display only key and value data? – Radhika Obhan Sep 11 '17 at 06:50
Not clear to me what format you're expecting in the output. "Key and value data" doesn't really narrow it down, I'm afraid. – Duncan Thacker Sep 11 '17 at 18:28

Ahmed Can Unbay · Answer 2 · 2017-09-10T20:12:33.713

0

You can use find() method to receive all of the objects from a schema.

var response;  

user.find({}, function(err, users){
       if(err) throw err;
       if(users.length != 0){
          response = users.map((user, i) => {
             return {
               index: i,
               name: user.name + ' ' + user.address
             };             
       }
    })
    for(var i = 0; i < response.length; i++){
       res.write('Key: ' i + ' the value: ' response[i] + '\n');
    }
    res.end();

You should also use res.json() once only, as it will return Can't set headers after they are sent error.

Please see this link for info on res.json()

edited Sep 10 '17 at 20:12

answered Sep 10 '17 at 19:48

Ahmed Can Unbay

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can we see your code? where does the `res` go to? @RadhikaObhan – Ahmed Can Unbay Sep 10 '17 at 19:59
@turmuka, you do the same as OP, trying to send response for each user. Use `map` to create an array of objects and after that send it. – alexmac Sep 10 '17 at 20:00
true, I just saw the mistake there, gonna edit it in a sec @alexmac – Ahmed Can Unbay Sep 10 '17 at 20:01

use for loop in node js?

2 Answers2