How can I update mysql2 query to not return undefined for return?-CodePudding

I am using nodejs and mysql2. I am storing all my queries inside a class. When I console.log the results I am able to view the data correctly, however when I use a return statment to return the data, I am getting undefined. I believe I need to use promises, but am uncertain how to do so correctly. Here is what I have currently which is returning undefined,

    viewManagerChoices() {
        const sql = `SELECT CONCAT(first_name, ' ',  last_name) AS manager, id FROM employee WHERE manager_id IS NULL`;
        db.query(sql, (err, rows) => {
        if (err) throw err;
           const managers = rows.map(manager => ({ name: manager.manager, value: manager.id }));
           managers.push({ name: 'None', value: null });
           return managers;
        });
    };

This is my attempt at using promises which is returning as Promise {<pending>},

viewManagers() {
        return new Promise((resolve, reject) => {
            const sql = `SELECT CONCAT(first_name, ' ',  last_name) AS manager FROM employee WHERE manager_id IS NULL`;
            db.query(sql,
                (error, results) => {
                    if (error) {
                        console.log('error', error);
                        reject(error);
                    }
                    const managers = [];
           for (let i = 0; i < results.length; i  ) {
               managers.push({ name: results[i].manager, value: i 1 });
           }
           managers.push({ name: "None", value: null });
                    resolve(managers);
                }
            
            )
        })
        
    }

My class is called Query and I am calling these methods by doing,

const query = new Query();
query.viewManagerChoices();
query.viewManagers();

CodePudding user response：

Your implementation for viewManagers is correct however promises don't make calls synchronous.

Either you need to use then callback or await the result in async context.

const query = new Query();
query.viewManagers().then((managers) => {
  // do stuff here
}).catch((error) => console.error(error.message));

async someFunc() {
  const query = new Query();
  try{
    const managers = await query.viewManagers();
  }catch(error){
    console.error(error.message);
  }
}

CodePudding user response：

use MySQL it's more easier for handling errors and data