How to replace callbacks with promises in Node.js?

To replace callbacks with promises in Node.js, we use the util.promisify method.

For instance, we write

const util = require("util");

const connectAsync = util.promisify(connection.connectAsync);
const queryAsync = util.promisify(connection.queryAsync);

exports.getUsersAsync = async () => {
  await connectAsync();
  return queryAsync("SELECT * FROM Users");
};

to call util.promisify with the connectAsync and queryAsync methods to convert them to functions that return promises.

And then we call connectAsync to return a promise and use await to run the promise.