"to hoist or not to hoist"

classdoesnothoist.js

var cat = new Cat() // it's ok !
cat.sayHello(); // then we call sayHello without any problem!

function Cat() { 
    this.sayHello = function() {
        console.log('hello Im a cat');
    }
}


var dog = new Dog(); // ref error wtf?
dog.SayHello();

class Dog {
   sayHello() {
     console.log('hello Im a dog');
   }
}