Correctly using promises with node-mysql

Question

I have been trying to do a simple query and return the results with node-mysql however I had several problems. Originally I wrote it where there was no promise, but if I tried to access user after just doing a query if returned undefined

The solution I came up with is the following, is this a good way of doing it? I need to wait until the results come back so I can then send a signal to the frontend to say the player is loaded and can play. Do I need to create a new promise for each query? I have a few tables I need to get data from (That can't be done with joins)

class Player {
 constructor(user_id, socket, connection) {
 this.socket = socket;
 this.connection = connection;
 this.loadUser(user_id)
 .then(() => {
 console.log("loaded user", this.user);
 });
 }
 async loadUser(user_id) {
 let _self = this;
 return new Promise((resolve, reject) => {
 _self.connection.query(`SELECT * FROM users WHERE id = ${user_id}`, (err, res) => {
 this.user = res[0];
 resolve()
 });
 })
 }
}
```

• Sᴀᴍ Onᴇᴌᴀ: Is node-mysql that the package @node-mysql/mysql?
• Ian: No it's github.com/mysqljs/mysql
• GirkovArpa: Async constructors would solve your problem easily if JavaScript supported them. There's a proposal here: github.com/tc39/proposal-async-init

Answer 1

Remove the async method call from the constructor, and make the async method return the instance (this):

class Player {
 constructor(user_id, socket, connection) {
 this.socket = socket;
 this.connection = connection;
 }
 async loadUser() {
 let _self = this;
 return new Promise((resolve, reject) => {
 _self.connection.query(`SELECT * FROM users WHERE id = ${this.user_id}`, (err, res) => {
 this.user = res[0];
 resolve(this)
 });
 })
 }
}

Then you can instantiate a new Player and wait for it to load the necessary data from the database, all in one line, like this:

const player = await new Player(user_id, socket, connection).loadUser();

Or like this:

new Player(user_id, socket, connection).loadUser().then(player => {
});