Leveraging Promises to Process MySQL Return Values in Node.js

In transitioning from Python to Node.js, the asynchronous nature of Node.js can present challenges. Consider a scenario where you need to return a value from a MySQL function, such as getLastRecord(name).

Traditionally, Node.js uses callbacks for asynchronous operations. However, to handle the asynchronous nature of getLastRecord(), we'll leverage Promises.

To implement the function using a Promise:

function getLastRecord(name) {
  return new Promise((resolve, reject) => {
    // Setup MySQL connection and query
    // ...

    connection.query(query_str, query_var, (err, rows, fields) => {
      if (err) {
        return reject(err); // Handle error
      }
      resolve(rows); // Resolve with results
    }); // Callback function
  });
}

To handle the returned value, you can chain .then() and .catch() callbacks to the Promise:

getLastRecord('name_record')
  .then((rows) => {
    // Handle returned rows here
    console.log(rows);
  })
  .catch((err) => {
    // Handle errors here
    console.log(err);
  });

You can also implement the conditional check:

getLastRecord('name_record')
  .then((rows) => {
    if (rows.length > 20) {
      console.log('action');
    }
  });

By adopting Promises in this scenario, you introduce a more structured and readable approach to handling asynchronous operations, ensuring a cleaner and more maintainable codebase.