将 node.js postgres 查询结果保存在变量中

Question

I am trying to save some user_ids from my database in an array so that I can check against that array in a route. The callback function logs the correct data but the value of the const stays undefined. Does anybody have any ideas on how to solve this problem?

I am using the node-postgres library to connect to the database.

This is my code:

database query function:

const getAll = (callback) => {
  const query = `SELECT user_id FROM users`;

  pool
    .query(query)
    .then(data => {
      callback(null,data.rows)
    })
    .catch(e => console.error(e.stack))
}

const with callback function:

const users = db.getAll(function(err,data) {
  if (err) {
    console.log(err);            
  } else {            
    const ids = data.map(x => x.user_id)
    console.log(ids);  // logs an array of ids 
    return ids         
  }    
})

console.log(users) // returns undefined

Any help is very much appreciated.

Answer 1

What's happening in your console log is executing before your callback has completed. To get this to work as you expect you want to refactor to use async/await or promises.