How to declare a function in the form of Arrow Function?

Question

How to declare the function below as Arrow Function in javascript Ecma 6 and then call it? Currently I use it like this and do not know how it leaves working without the "Function" in front.

execSQLQuery('DELETE FROM Usuarios WHERE idUser=' + parseInt(req.params.id), res);


function execSQLQuery(sqlQry, res){
       const connection = mysql.createConnection({
        host     : 'localhost',
        port     : 3306,
        user     : 'joao',
        password : '123',
        database : 'dadosD'
    })   
    connection.query(sqlQry, (error, results, fields)=>{
        if(error) 
          res.json(error);
        else
          res.json(results);
        connection.end();
        console.log('executou!');
    })
  };

Answer 1

I don’t think there’s any need to do that, it won’t make any difference in the code. But...

Arrow functions are anonymous functions, that is, they have no name. To identify them, you need to assign it to some label, in case a variable.

That way:

const execSQLQuery = (sqlQry, res) => {
...
};

But if you do, you will have a ReferenceError, whereas statements let or const has not Hoisting. Therefore, you have to move the declaration to before invoking it. In case:

const execSQLQuery = (sqlQry, res) => {
...
};

execSQLQuery('DELETE FROM Usuarios WHERE idUser=' + parseInt(req.params.id), res);

(Note that you are now below)