Impelement promise in JS - node.js

Question

I have a function located in /models/profile.js:
module.exports = {
getDataProfil : function(id_user){
connection.query("SELECT * FROM user WHERE id_user = ?", [id_user], function(err, rows, fields){
if(err) throw err;
console.log(rows[0]);
});
}
}
I want to call the getDataProfile inside /controllers/profile.js
module.exports.profil_get = function(req, res, next) {
profile_model.getDataProfil(req.user.id_user).then();
}
I want to implement promise there, since I need to render the page. How to do it? Thankyou

Answer 1

Use this, You can also use q module too.
module.exports = {
getDataProfil: function(id_user) {
connection.query("SELECT * FROM user WHERE id_user = ?", [id_user], function(err, rows, fields) {
if (err) return ['err', err];
return [null, rows[0]];
});
}
}
And profil_get will be:
module.exports.profil_get = function(req, res, next) {
profile_model.getDataProfil(req.user.id_user)
.then(function(res) {
console.log(res);
});
}
Check if res[0] is null for success or is a string for rejection.
Another implementation is
module.exports = {
getDataProfil: function(id_user) {
var dfd = q.defer();
connection.query("SELECT * FROM user WHERE id_user = ?", [id_user], function(err, rows, fields) {
if (err) { dfd.reject(err); }
else { dfd.resolve(rows[0]); }
});
}
return dfd.promise;
}
And profil_get:
module.exports.profil_get = function(req, res, next) {
profile_model.getDataProfil(req.user.id_user)
.then(function(res) {
console.log(res);
})
.catch(function(err){
console.log(err);
});
}

Answer 2

Using native promises:
module.exports = {
getDataProfile : function ( id_user ) {
return new Promise( ( resolve, reject ) => {
connection.query( 'SELECT * FROM user WHERE id_user = ?', [ id_user ], function ( err, rows, fields ) {
if ( err ) {
return reject( err );
}
return resolve( rows[ 0 ] );
} );
} );
}
};
You can then call your promise and handle response/error cases. Ideally, you would respond to a client instead of using console.log/error:
module.exports.profile_get = function(req, res, next) {
profile_model.getDataProfile(req.user.id_user).then( response => {
console.log( response );
}).catch( err => {
console.error( err );
});
};

Answer 3

Just use native Promise constructor:
module.exports = {
getDataProfil : function(id_user) {
return new Promise(function (resolve, reject) {
connection.query("SELECT * FROM user WHERE id_user = ?", [id_user], function (err, rows, fields) {
if (err) return reject(err);
return resolve(rows[0]);
});
})
}
}