Add examples

examples/guess-the-number/game.js

@@ -0,0 +1,33 @@
+export class Game {
+  /**
+   * A number guessing game.
+   * @param {number} minimum - The minimum number to guess.
+   * @param {number} maximum - The maximum number to guess.
+   */
+  constructor(minimum, maximum) {
+    this.secretNumber = Math.ceil(Math.random() * maximum - minimum) + minimum;
+    this.guesses = new Set();
+
+    console.log(`Guess the number between ${minimum} and ${maximum}.`);
+  }
+
+  /**
+   * Make a guess for the secret number.
+   * @param {number} number - The number to guess.
+   */
+  guess(number) {
+    if (this.guesses.has(number)) {
+      return 'You already guessed that number!';
+    }
+
+    this.guesses.add(number);
+
+    if (number < this.secretNumber) {
+      return 'Too low!';
+    } else if (number > this.secretNumber) {
+      return 'Too high!';
+    } else if (number === this.secretNumber) {
+      return `Correct! You guessed the number in ${this.guesses.size} attempts.`;
+    }
+  }
+}