How to Convert Asynchronous MySQL Operations to Promises in Node.js?

Converting Asynchronous MySQL Operations to Promises in Node.js

Node.js's asynchronous nature poses a challenge for developers coming from Python. To address this, this code snippet attempts to wrap a MySQL operation inside an asynchronous function that returns a value. However, this approach won't work due to the asynchronous nature of Node.js.

To resolve this issue, the operation needs to be refactored to return a promise. Using Bluebird, this can be achieved as follows:

<code class="javascript">function getLastRecord(name) {
  return new Promise((resolve, reject) => {
    // Establish a connection to MySQL
    const connection = getMySQL_connection();

    // Construct and execute the MySQL query
    const query_str = `SELECT name, FROM records WHERE (name = ?) LIMIT 1`;
    const query_var = [name];
    connection.query(query_str, query_var, (err, rows, fields) => {
      if (err) {
        return reject(err);
      }
      resolve(rows);
    });
  });
}</code>

Now, you can handle the returned rows as desired:

<code class="javascript">getLastRecord('name_record').then((rows) => {
  // Access the rows and perform operations

  if (rows.length > 20) {
    console.log("action");
  }
}).catch((err) => {
  // Handle any errors
  setImmediate(() => { throw err; });
});</code>

This approach ensures that the operation is executed asynchronously, while allowing you to handle the returned value in a synchronous manner using promises.

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