I have a web formulary from where i extract data. The unique field should be the email, but if i repeat the email my formulary breaks and throws error, i don't know how to stop my formulary to break, i just want a error.push("reenter your email"), withouth connecting again to the db using npm start. I am looking for a validation or smth, i am beginner into node.js and working with js

connection.query(
    "SELECT * FROM `employees` WHERE `email`= ?",
    [employee.email],
    function (err, row) {
      if (err) throw err;
      else {
        if (row && row.length) {
          error.push("Email already exists!"); //this does nothing
          return console.log("Email is existing already!");
        }
      }
    }
  );
if(error.length === 0){
          // insert data in the table
}
else {
    res.status(400).send(error);
    console.log("Error");
  }

I want error.push("Email already exists!"); to modify my error array so it won't enter in the first if(error.length === 0)

CodePudding user response：

connection.query is an asynchronous function. So error.push happens after your if.

Possible solutions -

1. Move the further code into the callback function
2. Create a Promise and resolve it in the function, aka use the async/await system. Example function:

const executeQuery = (con, query, params = null) => {
    return new Promise((resolve, reject) => {
        con.query(query, params, (err, res) => {
            if (err) {
                reject(err);
                return
            }
            resolve(res);
        });
    })
};

You can run this, and you can say await executeQuery(con,query,param) and proceed from there.