mixins and composition

mixins_and_composition.js

function compose(...fns) {
  return arg => fns.reduceRight((prev, curr) => curr(prev), arg);
}

const fatherMixin = (BaseClass = class {}) =>
  class Father extends BaseClass {
    constructor() {
      super()
      this.frontendLang = 'JavaScript';
    }
  };

const motherMixin = (BaseClass = class {}) =>
  class Mother extends BaseClass {
    constructor() {
      super()
      this.backendLang = 'Elixir';
    }
  };

const secretGun = Symbol(); // To be used as a private class method

const Parents = compose(fatherMixin, motherMixin)();

class Child extends Parents {
  constructor(mothersSurname, fathersSurame) {
    super()
    this.name = `John ${mothersSurname} ${fathersSurame}`;
  }

  [secretGun]() { // class method using Symbol.
    const gun = [
      '\n..._...|..____________________, ,)',
      '\n....../ `---___________----_____|]',
      '\n...../_==o;;;;;;;;_______.:/',
      '\n.....), ---.(_(__) / ',
      '\n....// (..) ), ----" ',
      '\n...//___// ',
      '\n..//___//',
      '\n.//___//'
    ];
    console.warn(...gun);
  }
};

const child = new Child('Mom', 'Dad');

console.log(child);
// It logs Child { backendLang: 'Elixir', frontendLang: 'JavaScript', name: 'John Mom Dad' }

child[secretGun]();
/* The secretGun() method cannot be called using dot notation.
 * Unless you export/import the secretGun Symbol you won't be
 * able to call this method.
 */