thisRules.js

// https://github.com/getify/You-Dont-Know-JS/blob/master/this%20%26%20object%20prototypes/ch2.md
/*
 * Called with new? Use the newly constructed object
 */
class Pokemon {
  constructor(hp, mp) {
    this.hp = hp;
    this.mp = mp;
  } 
}

const pokemon1 = new Pokemon(100, 100);
const pokemon2 = new Pokemon(0, 0);

console.log(pokemon1.hp); // 100
console.log(pokemon2.hp); // 0


/*
 * Called with call or apply (or bind)? Use the specified object.
 */
function pokemon() {
  console.log(this.hp);
}

const charmander = { hp: 100 };

pokemon.call(charmander);

/*
 * Called with context object owning the call? Use the context object
 */

function pokemon() {
  console.log(this.hp);
}

const squirtle = {
  hp: 100,
  pokemon: pokemon
};

const bulbasaur = {
  hp: 0,
  squirtle: squirtle
};

console.log(squirtle.pokemon()); // 100
console.log(bulbasaur.squirtle.pokemon()); // 100

/*
 * Default: undefined in strict mode, global otherwise.
 */
function pokemon() {
  console.log(this.hp);
}

var hp = 100;

pokemon(); // 100