Giving a class something it can do

01 / 04

Not only data but doing

The classes so far only settled "what values it holds".

But a real one has things it can do as well. A robot can greet you; an order can work out its amount. Those "things it can do" go on the blueprint too.

02 / 04

How to write a method

Write name() { } inside a class's { }. This is called a method — a function the class owns.

You do not write function. To call it you write instance.methodName(), with a ( ) on the end.

class Robot {  hello() {    console.log("beep boop");  }}const r = new Robot();r.hello();

Result

beep boop

03 / 04

Parameters and return values both work

A method is one of the function family, so it can catch parameters and send values back with return.

What comes back is an ordinary value. You can show it or use it in a sum as it stands.

class Machine {  double(n) {    return n * 2;  }}const m = new Machine();console.log(m.double(7));

Result

04 / 04

Written alongside the constructor

The constructor and the methods sit side by side in the same { }. No , between them (that is where it differs from an object literal).

Write as many methods as you like. Think of it as the place where you line up "the things anything made from this blueprint can do". Off you go.

class Robot {  constructor(name) {    this.name = name;  }  greet() {    console.log("beep boop");  }}const r = new Robot("Clank");console.log(r.name);r.greet();

Result

Clank
beep boop