How to save records to db in a loop on node.js?

Question

Node.js

I receive an array of data. There is a task - to save the obtained values ​​​​to the mysql database. At the same time, the field in the database is unique, so you need to skip duplicates and save the next unique values. But I just can’t cope with asynchrony in cycles and promises. What am I doing wrong?

let data = ;

const queryStart = (item) => {
    const sql = `INSERT INTO domain (domain) VALUES ${item}`;
    return new Promise((res, rej) => {
      connection.query(sql, (error, result) => {
        if(error.code == "ER_DUP_ENTRY") return rej(new Error('Такая запись уже есть'));
        return res(result);
      });
    });
}

for(var item for data) {
  queryStart(item).then(
    result => {
      console.log(result)
      process.exit();
    },
    error => {
      console.log(error)
      process.exit();
    }
  );
}

Answer 1

First, in NodeJS, remove the duplicates from the array.
Second, at the database level, declare unique keys.
And may ASCID be with you