Can't put rows into array using sqlite3 on Node.js

Question

I have a code in Node.js that selects everything from a SQLite Database and print every row and it works, here's the code:

var sqlite3=require('sqlite3').verbose();

var db=new sqlite3.Database('./database.db',(err)=>{
    if(err){
        return console.error(err.message);
    }
    console.log('Connected...');
});

db.all('SELECT * FROM langs ORDER BY name',[],(err,rows)=>{
    if(err){
        return console.error(err.message);
    }
    rows.forEach((row)=>{
        console.log(row.name);
    });
});

db.close((err) => {
    if (err) {
        return console.error(err.message);
    }
    console.log('Database closed...');
});

It prints:

Connected...
C
Java
Database closed...

But when I try using this to get the rows into an array, it doesnt work:

var data=[];
db.all('SELECT * FROM langs ORDER BY name',[],(err,rows)=>{
    if(err){
        return console.error(err.message);
    }
    rows.forEach((row)=>{
        data.push(row);
    });
});

for(col in data){
    console.log(col.name);
}

It prints:

Connected...
Database closed...

SOLUTION: After modifying the code to work with async/await and updating Node to version 8.11.1, it works, code:

var data=[],records=[];

function getRecords(){
    return new Promise(resolve=>{
        db.all('SELECT * FROM langs ORDER BY name',[],(err,rows)=>{
            if(err){
                return console.error(err.message);
            }
            rows.forEach((row)=>{
                data.push(row);
            });

            resolve(data);
        });
    });
}

async function asyncCall(){
    records=await getRecords();

    records.forEach(e=>{
        console.log(e.name);
    });
}

asyncCall();

i may be missing something, but it looks like you don't have a console.log statement in your second implementation. did you want to print something specific? ... my mistake i see it now. — egnomerator
– egnomerator, Commented May 3, 2018 at 23:10

Muhammad Usman · Accepted Answer · 2018-05-03 23:25:25Z

3

This is because db.all is asynchronous. Data array is not yet populated and you are trying to loop through it. Just move for loop inside and you're done.

Your final code should look like

var data=[],
     records = [];
function getRecords(){
  return new Promise((resolve,reject)=>{
  db.all('SELECT * FROM langs ORDER BY name',[],(err,rows)=>{
    if(err){
        return console.error(err.message);
    }
    rows.forEach((row)=>{
        data.push(row);
    });
    
   resolve(data);
})
  
  })
}

(async function(){
  records = await getRecords();
})()

ps. It is not good idea to use for(..in..) you better use forEach

edited May 3, 2018 at 23:25

answered May 3, 2018 at 23:12

Muhammad Usman

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6 Comments

DarkCeptor44 Over a year ago

I need to pass that array through WebSocket, so I will need to put everything in there?

Muhammad Usman Over a year ago

you can use async/await to get the data and use it where you want

Muhammad Usman Over a year ago

well, I've updated as per to async/await. Now you can use records whenever you want

DarkCeptor44 Over a year ago

It gave me this error: (async function(){ ^^^^^^^^ SyntaxError: Unexpected token function at createScript (vm.js:56:10) at Object.runInThisContext (vm.js:97:10) at Module._compile (module.js:542:28) at Object.Module._extensions..js (module.js:579:10) at Module.load (module.js:487:32) at tryModuleLoad (module.js:446:12) at Function.Module._load (module.js:438:3) at Module.runMain (module.js:604:10) at run (bootstrap_node.js:393:7) at startup (bootstrap_node.js:150:9)

Muhammad Usman Over a year ago

there may be some syntax issue. try matching it with developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

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