One response after few async functions - mysql

Question

I have a web page with a form where a user can edit personal info, education, work history and etc.
And the user can add more than one degree, for example: bs, ms, phd. And a few job positions as well.
When the user push 'save' button I send all this data to my server. I send it all in one request. In the server I have a point to handle the request.
app.post(config.version + '/profile', (req, res, next) => {});
And there I do a few MySQL queries to insert/update/delete a data. I use mysql package from npm to do that.
new Promise((resolve, reject) => {
const userQuery = `INSERT INTO user ...;`;
const degreesQuery = 'INSERT INTO degree ...;';
const positionsQuery = 'UPDATE position SET ...;';
this.connection.query(userQuery, err => {});
this.connection.query(degreesQuery, err => {});
this.connection.query(positionsQuery, err => {});
resolve({});
})
In the end I do resolve({}) but I want to select updated profile and send it back (because in MySQL tables for degrees I add ids that helps me to not insert again duplicate data). So, my question is how to do resolve({}) only when all my async this.connection.querys finished?

Answer 1

My suggestion is to run all the queries in a Promise.all().
Example:
const queries = [
`INSERT INTO user ...;`;,
'INSERT INTO degree ...;',
'UPDATE position SET ...;'
];
Promise.all(queries.map((query) => {
return new Promise((resolve, reject) => {
this.connection.query(query, err => {
return err ? reject(err) : resolve();
});
});
})
.then(() => {
// continue
// get your updated data here with and send it as response
})
If your db library has support for Promise write it this way
Promise.all(queries.map((query) => {
return this.connection.query(query);
})
.then(() => {
// continue
// get your updated data here with and send it as response
})