I'm using nodejs, express, postgres as sql server. I created Javascript API that sends queries to the server, And i want when i send a multi-line insert query to the server if one or more of the lines already in the system the query will continue without those in the server And if foreign key error happen(is not present in table "tablename") it will ask the client(wait for response) if to add it to the foreign table and then continue with the query.

So far i did this code, but can not figure out where to start with this problem:

insert(){
    return new Promise( async (resolve, reject) => {
        const client = await this.PoolCONN.connect();

        client.query(query, (err, results)=>{
            
            if(err){
                const error = this.HandlError(err)
                client.release();
                return reject(error);
            };
            
            client.release();
            return resolve(results);

        });
    })
}

HandlError(error){
    const ErrorCode = error.code;
    let errorName = "";
    let msg = "";
    switch (ErrorCode) {
        case '23505': // duplicate values
            
            msg = ``;
            errorName = "duplicate";
            break;                
        case '23503': // foreign_key_violation
            msg = ``
            errorName = "foreign key"
            break;                
        default:
            break;
    }

    return {
        error: errorName,
        errorMSG: msg,
    }

}

NOTE: I know I'm asking for a lot I'm a bit lost