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Prototype VS Static, Getter, Setter


class Animal {
  constructor(n, a) {
    this.name = n; // prototype variable
    this.age = a; // prototype variable
  }

  eat() { // prototype method
    console.log(this.name + ' is eating.');
  }

  static comment() { // static method
    console.log('All animals are cute.');
  }

  whoami() {
    //this.constructor.eat();  // TypeError
    this.constructor.comment(); // this.constructor.staticFunction() allowed
    console.log('I am a nice ' + this.constructor.name + '.');
  }

  get intro() { // getter, to act like prototype variable
    return 'This is ' + this.name + '.';
  }

  set rename(n) { // setter
    this.name = n;
  }
}

Animal.prototype.sex = 'm'; // prototype variable
Animal.prototype.drink = function() {
  console.log(this.name + ' is drinking.');
}; // prototype method

Animal.message = 'We should protect all animals.'; // static variable
Animal.comment2 = () => console.log(Animal.message); // static method

var b = new Animal('Brownie', 5);
console.log(b.age, b.sex);
b.eat();
b.drink();
b.whoami();
Animal.comment();
Animal.comment2();
console.log(b.intro);
b.rename = 'Greenie';
b.drink();
console.log(typeof b);
console.log(b instanceof Animal);

//let m1=b.eat; m1();        // TypeError ('this' is undefined)
let m2 = Animal.comment;
m2();

5 "m" Brownie is eating. Brownie is drinking. All animals are cute. I am a nice Animal. All animals are cute. We should protect all animals. This is Brownie. Greenie is drinking. object true All animals are cute.

Note how you verify the class name of an object with instanceof.

A class declaration is not hoisted, ie. a class cannot be used before its declaration. Also, a class cannot be redeclared.