mysql node: can't set headers after they are sent - mysql

Question

I am trying to get a list of movies in a directory, parse titles, get movie information on TMDB than check if movie info is stored in mysql database and if not stored, insert info into the database.
I am using NodeJS/Express and mysql.
Here is my code so far:
exports.checkForMovies = function (req, res, next) {
const testFolder = './test/';
var movieList = [];
var movieResultsPromise = [];
var movieResults = [];
fs.readdirSync(testFolder).forEach(file => {
movieList.push(tnp(file));
});
movieList.forEach(movie => {
var waitPromise = searchTMDB(movie.title);
movieResultsPromise.push(waitPromise);
});
Promise.all(movieResultsPromise).then(result => {
movieResults = result;
movieResults.forEach(movie => {
checkMoviesInDB(movie.id, (err, data) => {
if (err) {
console.log(err)
}
if (data && data.update === true) {
var movieObj = {
m_tmdb_id: movie.id
};
insertMoviesToDB(movieObj, (resp, err) => {
if (err) {
console.log(err);
} else {
return res.json(resp);
}
});
} else {
return res.json(data);
}
});
});
});
}
function checkMoviesInDB(id, cb) {
var sql = "SELECT * FROM ?? WHERE m_tmdb_id = ?"
var table = ['movie', id];
sql = mysql.format(sql, table);
connection.query(sql, function (err, rows) {
if (err) {
return cb(err);
}
if (rows.length > 0) {
return cb(null, {
success: true,
update: false,
message: 'Movies up to date!'
})
} else {
return cb(null, {
update: true,
message: 'Updating database!'
})
}
});
}
function insertMoviesToDB(movie, cb) {
var sql = "INSERT INTO ?? SET ?";
var table = ['movie', movie];
sql = mysql.format(sql, table);
connection.query(sql, function (err, rows) {
if (err) {
return cb(err);
} else {
return cb(null, {
success: true,
message: 'Movie database updated!'
})
}
});
}
function searchTMDB(title) {
return new Promise((resolve, reject) => {
https.get(config.tmdbURL + title, response => {
var body = "";
response.setEncoding("utf8");
response.on("data", data => {
body += data;
});
response.on("end", () => {
body = JSON.parse(body);
resolve(body.results[0]);
});
response.on("error", (err) => {
reject(err);
});
});
});
}
After code execution it inserts movie info in the database or responses with "Movies up to date" but I am getting this error and NodeJS crashes:
Error: Can't set headers after they are sent.
Any help is appreciated, thanks!
EDIT!
This is the new code and I am still getting the same error...
exports.checkForMovies = function (req, res) {
const testFolder = './test/';
var movieList = [];
var movieResults = [];
fs.readdirSync(testFolder).forEach(file => {
movieList.push(tnp(file));
});
var movieObj = movieList.map(movie => {
var tmp = [];
return searchTMDB(movie.title).then(data => {
tmp.push(data);
return tmp
});
});
var checkDB = Promise.all(movieObj).then(moviesData => {
moviesData.map(movieData => {
checkMoviesInDB(movieData[0]).then(checkResponse => {
if (!checkResponse.movieToInsert) {
res.json(checkResponse);
} else {
var insertArray = checkResponse.movieToInsert;
var inserting = insertArray.map(movie => {
var movieObject = {
m_tmdb_id: movie.id,
m_name: movie.title,
m_year: movie.release_date,
m_desc: movie.overview,
m_genre: undefined,
m_poster: movie.poster_path,
m_watched: 0
};
insertMoviesToDB(movieObject).then(insertResponse => {
res.json(insertResponse);
});
});
}
});
});
});
}
function checkMoviesInDB(movie) {
var moviesToInsert = [];
return new Promise((resolve, reject) => {
var sql = "SELECT * FROM ?? WHERE m_tmdb_id = ?"
var table = ['movie', movie.id];
sql = mysql.format(sql, table);
connection.query(sql, function (err, rows) {
if (err) {
return reject(err);
}
if (rows.length === 0) {
moviesToInsert.push(movie);
resolve({
success: true,
movieToInsert: moviesToInsert
});
} else {
resolve({
success: true,
message: 'No movie to insert'
});
}
});
});
}
function insertMoviesToDB(movie) {
return new Promise((resolve, reject) => {
var sql = "INSERT INTO ?? SET ?";
var table = ['movie', movie];
sql = mysql.format(sql, table);
connection.query(sql, function (err, rows) {
if (err) {
return reject(err);
} else {
resolve({
success: true,
message: 'Movie added!'
});
}
});
});
}
function searchTMDB(title) {
return new Promise((resolve, reject) => {
https.get(config.tmdbURL + title, response => {
var body = "";
response.setEncoding("utf8");
response.on("data", data => {
body += data;
});
response.on("end", () => {
body = JSON.parse(body);
resolve(body.results[0]);
});
response.on("error", (err) => {
reject(err);
});
});
});
}
Auth.js
const config = require('./config');
const jwt = require('jsonwebtoken');
module.exports = function (req, res, next) {
var token = req.body.token || req.params.token || req.headers['x-access-token'];
if (token) {
jwt.verify(token, config.secret, function (err, decoded) {
if (err) {
return res.json({
success: false,
message: 'Failed to authenticate token.'
});
} else {
req.decoded = decoded;
next();
}
});
} else {
return res.status(403).send({
success: false,
message: 'Please login in to countinue!'
});
}
};

Answer 1

Hope this helps:
// Bad Way
const checkForMovies = (req, res) => {
const movieList = ['Braveheart', 'Highlander', 'Logan'];
movieList.forEach(movie => {
res.json(movie); // Will get Error on second loop: Can't set headers after they are sent.
})
}
// Good Way
const checkForMovies = (req, res) => {
const movieList = ['Braveheart', 'Highlander', 'Logan'];
const payload = { data: { movieList: [] } };
movieList.forEach(movie => {
payload.data.movieList.push(movie);
});
// send res once after the loop with aggregated data
res.json(payload);
}
/* GET home page. */
router.get('/', checkForMovies);