In Typescript, this and super are keywords used in object-oriented programming to refer to the current instance of a class and the base class, respectively.
This keyword
Definition: Refers to the current instance of the class.
Use Case:
- Access instance properties and methods.
- Call another method within the same class.
- Pass the current object as an argument
class Pizza {
name: string
constructor(name: string){
this.name = name;
}
cook():void{
console.log(`Start cooking ${this.name} pizza`)
}
}
const pepperoniPizza = new Pizza("pepperoni");
pepperoniPizza.cook();
super keyword
- Definition: Refers to the base class (the parent class) of the current class.
- Use Cases:
- Call the constructor of the base class.
- Access methods and properties from the base class
Example:
class Animal {
name: string;
constructor(name: string) {
this.name = name;
}
makeSound(): void {
console.log(`${this.name} makes a sound.`);
}
}
class Dog extends Animal {
constructor(name: string) {
super(name); // Calls the constructor of the base class
}
makeSound(): void {
super.makeSound(); // Calls the base class method
console.log(`${this.name} barks.`);
}
}
const dog = new Dog("Buddy");
dog.makeSound();
and the output include: makeSound() of Base Class is Animal and makeSound of subclass is Dog like this:
Buddy makes a sound. Buddy barks.
Key Points:
1. this:
- Alway refers to the current instance
- Can be used in constructor, method, or arrow functions.
- In arrow functions, this is lexically bound to the surrounding context.
*2. super: *
- Can only be used in classes that extend another class.
- Must be called in the constructor before accessing this in a derived class.
- Can be used to call parent class methods.
class Parent {
protected message: string = "Hello from Parent!";
}
class Child extends Parent {
showMessage(): void {
console.log(super.message); // Accesses the parent class property
}
}
const child = new Child();
child.showMessage(); // Output: Hello from Parent!
By using this and super correctly, you can manage inheritance and object behavior effectively in Typescript.
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