Methods and this

Learn to define methods inside a class and the this context.

Adding methods to a class

Adding a method to a class body looks like a function declaration, without the function keyword.

class User {
  greet() {
    return "Hello, " + this.name;
  }
}

The method can be called on any instance: u.greet(). Inside a method, this refers to the instance that called it.

The this context

Inside a method, this refers to the instance that called the method. This lets each instance use its own data.

const a = new User("Alex");
const b = new User("Sam");
a.greet(); // "Hello, Alex"
b.greet(); // "Hello, Sam"

The same method, called on different instances, binds this to a different object.

Exercise Counter class

Declare a Counter class. Its constructor sets this.count to 0. A method named increment increases this.count by one.

Show example solution

You can use this.count++ or this.count += 1.
Example solution:
class Counter {
  constructor() {
    this.count = 0;
  }
  increment() {
    this.count++;
  }
}

Test yourself

What does `this` refer to inside a method?
```
u.greet()
```
- the instance that called the method
- the class itself
- the global object
- the method name
Show answer

the instance that called the method — Correct! this binds to the instance that called the method.

Call the method

const u = new User("Alex");
u.____;

Show answer

const u = new User("Alex");
u.greet();

Match the concepts

method

function in the class body
this

refers to the calling instance
this.name

instance name property
u.greet()

method call

Next lesson: extends and super

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