How to display data to html div from mysql in nodejs?

Question

I use express as framework of nodejs, this is my ajax code on page member.ejs

function load_member(){
        $.ajax({
          url: '/load_member',
          success: function(r){
            console.log(r);
          }, error: function(){
            console.log('Error!');
          }
        });
      }

and this is my nodejs code (server.js)

var express = require('express');
var bodyParser = require('body-parser');

var app = express();

app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: false}));

app.set('view engine', 'ejs');

app.get('/load_member', function(req, res){
  var mysql = require('mysql');

  var con = mysql.createConnection({
    host: "localhost",
    user: "root",
    password: "root",
    database: 'db_node',
    port: '/Applications/MAMP/tmp/mysql/mysql.sock'
  });

  con.connect(function(err) {
      if (err) throw err;

      let sql = "SELECT * FROM users";
      con.query(sql, function (err, result) {
          if (err) throw err;

          result.forEach(value => {
            res.json({ data: result });
          });
      });
  });

});

I got this error from terminal

/Applications/MAMP/htdocs/nodejs/node_modules/mysql/lib/protocol/Parser.js:80
        throw err; // Rethrow non-MySQL errors
        ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:470:11)
    at ServerResponse.header (/Applications/MAMP/htdocs/nodejs/node_modules/express/lib/response.js:767:10)
    at ServerResponse.json (/Applications/MAMP/htdocs/nodejs/node_modules/express/lib/response.js:264:10)
    at result.forEach.value (/Applications/MAMP/htdocs/nodejs/server.js:46:17)
    at Array.forEach (<anonymous>)
    at Query.<anonymous> (/Applications/MAMP/htdocs/nodejs/server.js:45:18)
    at Query.<anonymous> (/Applications/MAMP/htdocs/nodejs/node_modules/mysql/lib/Connection.js:502:10)
    at Query._callback (/Applications/MAMP/htdocs/nodejs/node_modules/mysql/lib/Connection.js:468:16)
    at Query.Sequence.end (/Applications/MAMP/htdocs/nodejs/node_modules/mysql/lib/protocol/sequences/Sequence.js:83:24)

thank you very much for your help.

BENARD Patrick · Accepted Answer · 2019-01-13 17:58:01Z

2

Try with this, you cannot use res.json multiple times...

You'll iterate on the values in your view....

  con.connect(function(err) {
      if (err) throw err;

      let sql = "SELECT * FROM users";
      con.query(sql, function (err, result) {
          if (err) throw err;

            res.json({ data: result });
      });
  });

answered Jan 13, 2019 at 17:58

BENARD Patrick

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Comments

bazzells · Accepted Answer · 2019-01-13 17:57:48Z

0

Cannot set headers after they are sent indicates that for a single request, you are attempting to send multiple responses.

Iterating over your dataset to print it in the UI will need to happen on the client, rather than server.

answered Jan 13, 2019 at 17:57

bazzells

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