Best practice for transferring JavaScript variables

Question

Best practice for transferring JavaScript variables

I'm struggling to grasp how JavaScript handles variable passing. The code snippet below is being executed in an Express controller:

const {
      sessionID,
      defenderID,
      challengerID
    } = req.body;

    console.log('sessionID', sessionID);
    console.log('defenderID', defenderID);
    console.log('challengeID', challengerID);
    const newGame = await Game.start({
      session: sessionID,
      defender: defenderID,
      challenger: challengerID
    });

This code snippet references the following function definition:

gameSchema.statics.start = async (session, defender, challenger) => {
  const date = new Date();
  console.log('attempting to start a game');
  console.log('session', session);
  console.log('defender', defender);
  console.log('challenge', challenger);
  const newGame = new Game({
    defender: defender,
    challenger: challenger,
    startTime: date
  });
  newGame.session.push(session);
  return await newGame.save().then((game) => game);
}

The current output shows:

defenderID johndoe
challengeID somechallenge
attempting to start a game
session {
  session: '620c29582ac275bd67cd3cca',
  defender: 'johndoe',
  challenger: 'somechallenge'
}
defender undefined
challenge undefined

I am puzzled by this discrepancy since I have another piece of code that performs similar actions without any issues.

javascript express mongoose parameter-passing

Answer 1

Answer №1

The issue arises when passing down an object as a single argument to the Game.start method while expecting 3 arguments in the function declaration for session, defender, and challenger. This results in the object being displayed in the console log for session.

To rectify this, individual arguments should be passed when calling the method like so-

  const {
    sessionID,
    defenderID,
    challengerID
  } = req.body;

 console.log('sessionID', sessionID);
 console.log('defenderID', defenderID);
 console.log('challengeID', challengerID);
 
 const newGame = await Game.start(sessionID, defenderID, challengerID);

Alternatively, you can modify the function declaration to accept a single object argument and then destructure the properties as follows:

gameSchema.statics.start = async ({
 session, 
 defender, 
 challenger
}) => {
  const date = new Date();
  console.log('attempting to start a game');
  console.log('session', session);
  console.log('defender', defender);
  console.log('challenge', challenger);
  const newGame = new Game({
    defender: defender,
    challenger: challenger,
    startTime: date
  });
  newGame.session.push(session);
  return await newGame.save();
}

Subsequently, the method can be called as previously done:

const newGame = await Game.start({
  session: sessionID,
  defender: defenderID,
  challenger: challengerID
});

Furthermore, there is no need to utilize .then after .save() since the async await pattern is already in place, resulting in the saved game document being returned with await newGame.save().

return await newGame.save();

Answer 2

The issue arises when passing down an object as a single argument to the Game.start method while expecting 3 arguments in the function declaration for session, defender, and challenger. This results in the object being displayed in the console log for session.

To rectify this, individual arguments should be passed when calling the method like so-

  const {
    sessionID,
    defenderID,
    challengerID
  } = req.body;

 console.log('sessionID', sessionID);
 console.log('defenderID', defenderID);
 console.log('challengeID', challengerID);
 
 const newGame = await Game.start(sessionID, defenderID, challengerID);

Alternatively, you can modify the function declaration to accept a single object argument and then destructure the properties as follows:

gameSchema.statics.start = async ({
 session, 
 defender, 
 challenger
}) => {
  const date = new Date();
  console.log('attempting to start a game');
  console.log('session', session);
  console.log('defender', defender);
  console.log('challenge', challenger);
  const newGame = new Game({
    defender: defender,
    challenger: challenger,
    startTime: date
  });
  newGame.session.push(session);
  return await newGame.save();
}

Subsequently, the method can be called as previously done:

const newGame = await Game.start({
  session: sessionID,
  defender: defenderID,
  challenger: challengerID
});

Furthermore, there is no need to utilize .then after .save() since the async await pattern is already in place, resulting in the saved game document being returned with await newGame.save().

return await newGame.save();

Answer 3

Answer №2

The entire object is passed as the first argument, labeled as 'session':

{
      session: sessionID,
      defender: defenderID,
      challenger: challengerID
}

You have the option to modify the call to:

const freshStart = await Game.begin(sessionID, defenderID, challengerID);

Alternatively, you can redefine the method as:

async (obj) => {
...
const freshStart = new Game({
    defender: obj.defender,
    challenger: challenger,
    startTime: date
  });
...

Answer 4

The entire object is passed as the first argument, labeled as 'session':

{
      session: sessionID,
      defender: defenderID,
      challenger: challengerID
}

You have the option to modify the call to:

const freshStart = await Game.begin(sessionID, defenderID, challengerID);

Alternatively, you can redefine the method as:

async (obj) => {
...
const freshStart = new Game({
    defender: obj.defender,
    challenger: challenger,
    startTime: date
  });
...

Best practice for transferring JavaScript variables

Answer №1

Answer №2

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