CODEWITHSUNDEEP
node.jssqlite
nolags
nolags

Reputation: 633

sqlite3 nodejs get value from table

I've got the function getName in my db.js 

function getName(uid){
    db.all("SELECT name FROM table WHERE uid = ? ",  function (err){
        if(err){
            console.log(err);
        }else{
            console.log(this);
        }
    });
}

and I want to get the name and save it to var name in another file.

var uid = req.session.user; 

var name = db.getName(uid);
      console.log(name);

what is wrong about the db function getname why do I get undefined? Would be great if you could help me!

Upvotes: 4

Views: 18211

Answers (1)

Himani Agrawal
Himani Agrawal

Reputation: 1272

Returning data from an async function might return undefined as the database request might not have completed on execution of return statement.

function getName(uid, callback){
  var query = "SELECT name FROM table WHERE uid = " + uid;
  var name = null;
  db.all(query, function (err, rows) {
    if(err){
        console.log(err);
    }else{
      name = rows[0].name;
    }
  });
  return name; <--- this can be execute before db.all() if executed therefore returning null. This is because javascript runs asynchronously.
}

The result from database query needs to be passed in a callback or it can be saved in a global variable.

function getName(uid, callback){
  var query = "SELECT name FROM table WHERE uid = " + uid;
  db.all(query, function (err, rows) {
    if(err){
        console.log(err);
    }else{
        callback(rows[0].name);
    }
  });
}

In order to execute from another file:

function print(name) {
  console.log(name);
}
var uid = req.session.user;
getName(uid, print);

Upvotes: 5

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