app.post('/signUpWeb', function (req, res) {
  var reqBody = req.body;
  var email= reqBody.email;
  var password= reqBody.password;
  var fullName= reqBody.fullName;
  var webDbInsertion  = {email: email, password: password, fullName: fullName};

  // note here that "emailExists" is now a parameter in your function callback to your function.
  DButils.checkIfPKexists(connection, "webusersMail", "email", webDbInsertion.email, function( emailExists) {

    if(emailExists == false){
    DButils.insertInfoToDB(connection, "webusersMail" ,webDbInsertion);
    console.log("successfull signup");
    res.send("successfull signup");
    }else{
    console.log("signup failed, email: " + email + " allready exits");
    res.send("signup failed");
    }
    res.end();

  });
});







exports.checkIfPKexists=  function(dbConnection, tableName, PK, newPK, onDone){ // new parameter 'onDone' is a function
    var query = dbConnection.query('select count(*) as mailPkCount from ' +tableName+ ' where ' +PK+ ' = ?', newPK, function (err, row, result) {
    if (err) {
      console.error(err);
      return;
    }
    var count= row[0].mailPkCount;
    var bool = (count > 0);
    // only changed this here to call the callback with the results
    if( onDone)
    onDone( bool);
    });
  };