Nodejs异步可重用函数调用

Question

I have some problem developping my own Node.JS application. I'm new to this kind of code architecture and not so good with asynchronous as well.

I currently have an event in my index.js script, calling for another script database.js . This database script will handle every db call inside my application.

index.js

const db = require('database.js');

//Called when a userjoin the application, this is working well//
db.userJoinedFunction("username");

I was planning adding other function call inside my "userjoinedFunction". For example : establishing first the DB connection --> 2nd checking if the user is already inside the DB --> 3d if not, create the user entry --> 4 if yes, do welcome back message. Since I have to establish the DB connection multiple time, I wanted to reuse some code inside theses function like this :

database.js

module.exports.userJoinedFuntion = userJoinedFunction

function userjoinedFunction(username){
   Init_database_connection();
   if(UserAlreadySignedup(username)){
      WelcomeMessage(username);
   }
   else {
      AddUserToDatabase(username);
   }
}

but obviously i'm doing it wrong because asynchronous Node.js application can't be that simple... How can I have that type of reusable architecture ? Do you have articles I can read about the subject ?

Thank you very much for your help !

EDIT 29/05/2019

with the response of novomanish I tried this :

async fonction run(){
  await(call("number 1");
  await Init_database_connection();
  await(call("number 2");
}

async function call(text){
  console.log(text);
}

async function Init_database_connection(){
  db = new sqlite3.Database("path", sqlite.OPEN_READWRITE, (err) =>{
    if(err){ console.log(err); }
    else { console.log("DB Connected"); }
  });
}

my output are :

- number one
- number two
- DB Connected

I checked many article and documentation, I can't find a good way of reusing function inside a "main function" (like in my example : the function run()). And i'm surprised that waiting for finished DB query isn't apparently thing...

Answer 1

You need async/await in your functions. So the new code would look like:

async function Init_database_connection(){...}
...

async function userjoinedFunction(username){
   await Init_database_connection();
   if(await UserAlreadySignedup(username)){
      return WelcomeMessage(username);
   }
   return AddUserToDatabase(username);

}

Regarding your edit, Init_database_connection should have returned a promise for await to work, like this:

async function Init_database_connection(){
  return new Promise((resolve, reject)=>{
      db = new sqlite3.Database("path", sqlite.OPEN_READWRITE, (err) =>{
        if(err){ 
           console.log(err); 
           reject();
        }else { 
          console.log("DB Connected"); 
          resolve()
        }
      });
  })
}