如何使用 nodejs 将值传递给另一个函数？

Question

So, I am trying to make a thing with discord js and sqlite3 but I've been stuck on this one issue for the past few hours and I still do not understand how I would resolve it.

  client.countDB = function(discordID) {
    const arr = [];
    db.each(`SELECT count(DiscordID) FROM verification WHERE DiscordID = ${discordID}`, function(err, row){
      if(err){console.log(err); return 0;}
      arr.push(Object.values(row))
      return arr;
    })
    return arr[0];
  };

So I am trying to get data that is only available in db.each but I do not know how I would pass it out so I can return the expected value. I've already tried using global variables, putting it in a larger scope, and I still cannot figure out how to do it.

Sorry if I am confusing I'm not used to asking questions all the time.

Edit: Should have said I'm using the npm sqlite3 module. https://www.npmjs.com/package/sqlite3

Answer 1

wrap your code in a function to make it synchronous, reference

var deasync = require('deasync');

function syncFunc()
{

    let arr;
    client.countDB = function(discordID) {
        db.each(`SELECT count(DiscordID) FROM verification WHERE DiscordID = ${discordID}`, function(err, row){
          if(err){console.log(err); arr = null;return;}
          const tmp = []
          tmp.push(Object.values(row))
          arr = tmp;
        })
      };
    while((arr === undefined))
    {
         deasync.runLoopOnce();
    }
    return arr[0];
}

Answer 2

If you have data in query easiest way to do is using promise.

client.countDB = function(discordID) {
 return new Promise((resolve, reject) => {
  db.each(`SELECT count(DiscordID) FROM verification WHERE DiscordID = ${discordID}`, function(err, row){
    //if you want to throw as an error, reject promise with the incoming error as "reject(err)"
    if(err){console.log(err); return resolve(0);}
    arr.push(Object.values(row))
    return resolve(arr[0]);
  })
 })};

// You can use this as 
client.countDB('someId')
 .then(data => console.log(data))
 .catch(err => console.log(err));