In this chapter, get ready to level up your console application skills as we dive into the creation of an exciting Guess the Number game app. This interactive game will challenge players to exercise their intuition by guessing a randomly generated number within a predefined range. Along the way, we'll unravel the mysteries of fundamental concepts such as

• Random number generation;
• Input validation;
• User interaction;
• Even saving game results to a file.

Challenge

Imagine delving into an app that promises excitement and intrigue. Players are invited to guess a mysteriously chosen number within a predefined range. The app offers instant feedback on each guess and a meticulous tally of the attempts made.

This hands-on example is your chance to refine your skills in building CLI Apps and showcases the art of crafting interactive programs.

Resulting App

See the magic in action! Below is a GIF illustrating the exciting Guess the Number Game app that you'll be crafting:

Building a Guessing Game Console App

You're presented with two paths. The first option beckons you to embark on the journey without assistance, while the second offers a helpful guide to ensure your success. Whether you dive in boldly or follow the structured guide, you're in for a fascinating experience that will leave you with a functional and captivating console app.

Masterplan

• Step 1: Setup and Initializations;
• Step 2: Define Game Parameters;
• Step 3: Define Utility Functions;
• Step 4: Game Logic;
• Step 5: Save Game Result;
• Step 6: Start the Game;
• Conclusion;
• Full App Code.

Step 1: Setup and Initializations

Prepare the canvas by creating a new directory and a file named app.js. Within this file, we conjure the necessary modules:

const readline = require('readline');
const fs = require('fs').promises;

Create a Readline interface:

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

Explanation: We import the necessary modules: readline for user interaction and fs.promises for file operations. Then, we create a Readline interface named rl to handle input and output.

Step 2: Define Game Parameters

Set the minimum and maximum numbers:

const minNumber = 1;
const maxNumber = 100;

Generate the secret number:

const secretNumber =
  Math.floor(Math.random() * (maxNumber - minNumber + 1)) + minNumber;

Initialize the attempts counter:

let attempts = 0;

Explanation: We define the range of numbers (minNumber and maxNumber) within which the secret number will be generated. The secret number is randomly generated using Math.random() and assigned to secretNumber. The attempts variable is initialized to keep track of the user's attempts.

Step 3: Define Utility Functions

Equip with a utility function for impeccable validation:

function isValidGuess(guess) {
  return !isNaN(guess)
    && guess >= minNumber
    && guess <= maxNumber;
}

Explanation: The isValidGuess function checks whether the user's guess is a valid number within the specified range (minNumber to maxNumber).

Step 4: Game Logic

The game's core mechanics through the playGame function:

function playGame() {
  rl.question(`Guess a number between ${minNumber} and ${maxNumber}: `, guess => {
    if (isValidGuess(guess)) {
      attempts++;
      const guessNumber = parseInt(guess);

      if (guessNumber === secretNumber) {
        console.log(`Congratulations! You guessed the number in ${attempts} attempts.`);
        saveGameResult(`Player won in ${attempts} attempts.`);
        rl.close();
      } else if (guessNumber < secretNumber) {
        console.log('Try higher.');
        playGame();
      } else {
        console.log('Try lower.');
        playGame();
      }
    } else {
      console.log('Please enter a valid number within the specified range.');
      playGame();
    }
  });
}

Explanation: The playGame function forms the core game loop. It uses rl.question to prompt the user for a guess. If the guess is valid, the function checks if the guess matches the secret number. If not, it provides feedback to the user and continues the game loop recursively.

Step 5: Save Game Result

Implement the logic of saving the user's game achievements into the game_results.txt file.

async function saveGameResult(result) {
  try {
    await fs.appendFile('game_results.txt', `${result}\n`);
    console.log('Game result saved.');
  } catch (err) {
    console.log('Failed to save game result.');
  }
}

Explanation: The saveGameResult function uses fs.promises to append the game result to a file named game_results.txt. It provides feedback on the success or failure of saving the result.

Step 6: Start the Game

Create the welcome message and launch the game:

console.log('Welcome to the Guess the Number game!');
playGame();

Explanation: We display a welcome message and start the game loop by calling the playGame function.

Full App Code

const readline = require("readline");
const fs = require("fs").promises;

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
});

const minNumber = 1;
const maxNumber = 100;

const secretNumber =
  Math.floor(Math.random() * (maxNumber - minNumber + 1)) + minNumber;
let attempts = 0;

function isValidGuess(guess) {
  return !isNaN(guess) && guess >= minNumber && guess <= maxNumber;
}

function playGame() {
  rl.question(
    `Guess a number between ${minNumber} and ${maxNumber}: `,
    (guess) => {
      if (isValidGuess(guess)) {
        attempts++;
        const guessNumber = parseInt(guess);

        if (guessNumber === secretNumber) {
          console.log(
            `Congratulations! You guessed the number in ${attempts} attempts.`
          );
          saveGameResult(`Player won in ${attempts} attempts.`);
          rl.close();
        } else if (guessNumber < secretNumber) {
          console.log("Try higher.");
          playGame();
        } else {
          console.log("Try lower.");
          playGame();
        }
      } else {
        console.log("Please enter a valid number within the specified range.");
        playGame();
      }
    }
  );
}

async function saveGameResult(result) {
  try {
    await fs.appendFile("game_results.txt", `${result}\n`);
    console.log("Game result saved.");
  } catch (err) {
    console.log("Failed to save game result.");
  }
}

console.log("Welcome to the Guess the Number game!");
playGame();