The Prince Academy株式会社 | Real-World Applications: Decision Making in Action | Making Decisions: Conditional Statements (If, Else If, Else) | Introduction to Computer Algorithm: Data Structures, Complexity, and Optimization for Modern AI Systems

Conditional statements are the building blocks of decision-making in computer programs. They allow our code to react differently based on whether a certain condition is true or false. Think of it like this: if it's raining, take an umbrella; otherwise, leave it at home. This simple logic is what powers countless features we use every day.

Let's explore some real-world scenarios where conditional statements are indispensable:

E-commerce and Pricing: Online stores use conditionals to offer discounts. If a customer has a coupon code, apply the discount; otherwise, charge the full price. They can also use conditionals to determine shipping costs based on the order total or destination.

let price = 100;
let hasCoupon = true;
let finalPrice;

if (hasCoupon) {
  finalPrice = price * 0.9; // 10% discount
} else {
  finalPrice = price;
}

console.log('The final price is: $' + finalPrice);

User Authentication: When you log into a website or app, conditionals are at play. If the username and password match the stored credentials, grant access; otherwise, show an error message.

let enteredUsername = 'user123';
let storedUsername = 'user123';
let enteredPassword = 'password123';
let storedPassword = 'password123';

if (enteredUsername === storedUsername && enteredPassword === storedPassword) {
  console.log('Login successful! Welcome!');
} else {
  console.log('Invalid username or password. Please try again.');
}

Game Development: Games are rife with conditional logic. For instance, if a player's health drops to zero, the game ends. If a player collects a certain number of coins, they level up. If the player presses the jump button, make the character jump.

graph TD;
    A[Player health > 0] --> B{Player presses jump button?};
    B -- Yes --> C[Character jumps];
    B -- No --> D[Character stays put];
    C --> E[Update character position];
    D --> E;
    E --> F{Game over condition met?};
    F -- Yes --> G[End Game];
    F -- No --> A;

Data Validation: When a user submits a form, conditionals check if the data is valid. For example, if an email address doesn't contain an '@' symbol, it's invalid. If a phone number has fewer than 10 digits, it's incomplete.

let email = 'test.example.com';

if (email.includes('@')) {
  console.log('Email format is valid.');
} else {
  console.log('Email format is invalid. Please include an @ symbol.');
}

Personalized Content: Websites and apps can show different content based on user preferences or past behavior. If a user has previously liked 'science fiction' books, show them recommendations for sci-fi. If it's a user's birthday, display a special greeting.

let userPreference = 'fiction';
let day = 'Monday';
let isBirthday = false;

if (isBirthday) {
  console.log('Happy Birthday!');
} else if (userPreference === 'fiction') {
  console.log('Here are some popular fiction novels.');
} else {
  console.log('Explore our diverse collection!');
}

These examples highlight how fundamental conditional statements are. They empower our programs to be dynamic, responsive, and intelligent, adapting to various situations just like we do in our daily lives.

let price = 100; let hasCoupon = true; let finalPrice; if (hasCoupon) { finalPrice = price * 0.9; // 10% discount } else { finalPrice = price; } console.log('The final price is: $' + finalPrice);

let enteredUsername = 'user123'; let storedUsername = 'user123'; let enteredPassword = 'password123'; let storedPassword = 'password123'; if (enteredUsername === storedUsername && enteredPassword === storedPassword) { console.log('Login successful! Welcome!'); } else { console.log('Invalid username or password. Please try again.'); }

graph TD; A[Player health > 0] --> B{Player presses jump button?}; B -- Yes --> C[Character jumps]; B -- No --> D[Character stays put]; C --> E[Update character position]; D --> E; E --> F{Game over condition met?}; F -- Yes --> G[End Game]; F -- No --> A;

let userPreference = 'fiction'; let day = 'Monday'; let isBirthday = false; if (isBirthday) { console.log('Happy Birthday!'); } else if (userPreference === 'fiction') { console.log('Here are some popular fiction novels.'); } else { console.log('Explore our diverse collection!'); }