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