Inheritance

What is inheritance?

Inheritance allows classes to acquire properties and methods from parent classes. Child classes can reuse parent code and add their own specialized behavior.

Benefits of inheritance?

• Reuse code from parent classes
• Create specialized versions of general classes
• Reduce code duplication
• Organize classes in hierarchies
• Share common functionality

// Parent class
class Character {
    constructor(name, health) {
        this.name = name;
        this.health = health;
    }
    takeDamage(damage) {
        this.health -= damage;
    }
}

// Child class inherits from parent
class Guard extends Character {
    constructor(name, health, weapon) {
        super(name, health);
        this.weapon = weapon;
    }
}

const guard = new Guard("Guard", 100, "sword");
guard.takeDamage(10);
console.log(guard.name + " has " + guard.health + " health and weapon: " + guard.weapon);

What does this code do?

• Character is parent class with basic properties
• Guard extends Character to inherit its methods
• Guard adds its own weapon property
• super() calls parent constructor
• Child class reuses parent code while adding specialization

// More examples from collisions-mechanic
class Entity {
    constructor(x, y) {
        this.x = x;
        this.y = y;
    }
    move(dx, dy) {
        this.x += dx;
        this.y += dy;
    }
}

class Player extends Entity {
    constructor(x, y, score) {
        super(x, y);
        this.score = score;
    }
}

const player = new Player(100, 300, 0);
player.move(10, 0);
console.log(player.x); // 110

What does this code do?

• Entity class has common movement method
• Player inherits move() from Entity
• Player adds its own score property
• Shows how child classes reuse parent functionality
• Demonstrates practical game hierarchy: generic entities with specialized versions

Try It Yourself

%%js // CODE_RUNNER: inheritence class Entity { constructor(x, y) { this.x = x; this.y = y; } } class Enemy extends Entity { constructor(x, y, type) { super(x, y); this.type = type; } } const goblin = new Enemy(100, 200, “Goblin”); console.log(goblin.type, goblin.x);