tcd <-> inter.com mentoring - high-low card game

index.js

// importing readline library - basically a scanner equivalent
const readlineSync = require('readline-sync');

// define our number of guesses required to win as a constant
const winningNumberOfGuesses = 4;

// define a function that takes an integer card number and returns the english
// name string for that card 2->"2", 10->"Jack", etc.
// how you implement this doesn't matter all that much - here I've defined a
// hash of number to card name pairs and used the funtion's cardNum parameter
// to perform a lookup in this hash.
// this hash could just as easibly be defined as a constant
const cardToString = (cardNum) => {
  return {
    2: '2',
    3: '3',
    4: '4',
    5: '5',
    6: '6',
    7: '7',
    8: '8',
    9: '9',
    10: 'Jack',
    11: 'Queen',
    12: 'King',
    13: 'Ace',
  }[cardNum]
};

// define a function that returns a random number between 2 and 13 (inclusive)
// you could implement this using `import java.util.Random;` in the java world
const chooseRandomCard = () => {
  const min = 2;
  const max = 13;
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

// declare some variables we're going to be using later in the loop
let currentCard;
let nextCard;
let correctGuessCount = 0;

// pick the first card and print it to the console - we need to do this outside
// the loop so that we have an initial value for the card
currentCard = chooseRandomCard();
console.log(`The card is a ${cardToString(currentCard)}`);

while (correctGuessCount < winningNumberOfGuesses) {
  let currentGuess;
  let hasValidInput = false;

  // implement error handling on the input - keep asking the user for input
  // until they give us either "higher" or "lower"
  while (!hasValidInput) {
    // you would use scanner here insead of readline - this basically just
    // prints the string "Do you think ...", reads the user input, and stores
    // it in the variable `currentGuess`
    currentGuess = readlineSync.question('Do you think the next card will be higher, lower or equal? ');
    if (currentGuess === "higher" || currentGuess === "lower") {
      // if the input was valid, set `hasValidInput` to true so that we exit
      // this inner loop and accept the input (stored in `currentGuess` above)
      hasValidInput = true;
    } else {
      console.log(`${currentGuess} is not a valid input - please choose "higher" or "lower"`);
    }
  }

  // Boolean: encode whether the current guess thought the next card would be
  // higher here - if the guess was not "higher" then it was "lower"
  const guessIsThatNextCardWillBeHigher = currentGuess === "higher";

  // pick the next random card
  nextCard = chooseRandomCard();

  // Boolean: check if the current card is lower or higher than the next card
  const nextCardIsHigher = nextCard > currentCard;

  // Boolean: if the user's guess matches the outcome of the high/low check
  const guessWasCorrect = guessIsThatNextCardWillBeHigher === nextCardIsHigher;

  // prepare the next iteration of the loop by setting the currentCard variable
  currentCard = nextCard;
  // having this print here (instead of below the if(guessWasCorrect) statement
  // at the end of the loop) allows us to show the user what the last card was
  console.log(`The card is a ${cardToString(currentCard)}`);

  if (guessWasCorrect) {
    // increment our correct guess tally so that we will exit the loop when we
    // hit 4
    correctGuessCount++;
  } else {
    // mock the user for losing
    console.log('Oh no, you done goofed. Game over.')
    // you would use System.exit()
    process.exit()
  }
}

// if code execution ever gets to here (ie. we were able to exit the loop) then
// we must have won - because if at any point we guessed incorrectly the
// program would have terminated prematurely (in the `process.exit()` line above)
console.log('Congratulations. You got them all correct.');