May 5, 2020 · May 8, 2020
diff --git a/1-js/09-classes/02-class-inheritance/1-class-constructor-error/solution.md b/1-js/09-classes/02-class-inheritance/1-class-constructor-error/solution.md
 That's because the child constructormust call `super()`.
 Eso es porque el constructorhijo debe llamar a `super()`.

 Here's the corrected code:
 Aqui está el código corregido:

 ```js run
 class Animal {
 }

 *!*
 let rabbit = new Rabbit("White Rabbit"); //ok now
 let rabbit = new Rabbit("Conejo Blanco"); //bueno ahora
 */!*
 alert(rabbit.name); //White Rabbit
 alert(rabbit.name); //Conejo Blanco
 ```
diff --git a/1-js/09-classes/02-class-inheritance/1-class-constructor-error/task.md b/1-js/09-classes/02-class-inheritance/1-class-constructor-error/task.md

 ---

 # Errorcreating an instance
 # Erroral crear una instancia

 Here's the code with`Rabbit`extending`Animal`.
 Aquí está el código de la clase`Rabbit`que extiende a`Animal`.

 Unfortunately,`Rabbit`objects can't be created. What's wrong? Fix it.
 Desafortunadamente, los objetos`Rabbit`no se pueden crear. ¿Que pasa? Arréglalo.
 ```js run
 class Animal {

 }

 *!*
 let rabbit = new Rabbit("White Rabbit"); // Error:this is not defined
 let rabbit = new Rabbit("Conejo Blanco"); // Error:esto no está definido
 */!*
 alert(rabbit.name);
 ```
diff --git a/1-js/09-classes/02-class-inheritance/2-clock-class-extended/solution.view/extended-clock.js b/1-js/09-classes/02-class-inheritance/2-clock-class-extended/solution.view/extended-clock.js
 class ExtendedClock extends Clock {
  constructor(options) {
    super(options);
    let { precision=1000 } = options;
    let { precision =1000 } = options;
    this.precision = precision;
  }

diff --git a/1-js/09-classes/02-class-inheritance/2-clock-class-extended/source.view/index.html b/1-js/09-classes/02-class-inheritance/2-clock-class-extended/source.view/index.html
  clock.start();


  /*Your class should work like this: */
  /*Tu clase debería funcionar así: */

  /*

diff --git a/1-js/09-classes/02-class-inheritance/2-clock-class-extended/task.md b/1-js/09-classes/02-class-inheritance/2-clock-class-extended/task.md

 ---

 #Extended clock
 #Reloj extendido

 We've got a `Clock` class. As of now, it prints the time every second.
 Tenemos una clase de 'Clock'. A partir de ahora, imprime la hora cada segundo.


 [js src="source.view/clock.js"]

 Create a new class `ExtendedClock`that inherits from `Clock`and adds the parameter `precision` -- the number of `ms` between "ticks".Should be `1000` (1second) by default.
 Crea una nueva clase `ExtendedClock`que herede de `Clock`y agrega el parámetro `precision`: este es el número de `milisegundos` entre "tics".Debe ser `1000` (1segundo) por defecto.

 -Your code should be in the file `extended-clock.js`
 -Don't modify the original`clock.js`. Extend it.
 -Tu código debe estar en el archivo `extended-clock.js`
 -No modifiques el`clock.js` original. Extiéndelo.
diff --git a/...09-classes/02-class-inheritance/3-class-extend-object/rabbit-extends-object.svg b/...09-classes/02-class-inheritance/3-class-extend-object/rabbit-extends-object.svg
diff --git a/1-js/09-classes/02-class-inheritance/3-class-extend-object/solution.md b/1-js/09-classes/02-class-inheritance/3-class-extend-object/solution.md
 First, let's see why the latter code doesn't work.
 Primero, veamos por qué el último código no funciona.

 The reason becomes obvious if we try to run it. An inheriting class constructor must call`super()`.Otherwise`"this"`won't be "defined".
 La razón se vuelve obvia si tratamos de ejecutarlo. Un constructor de clase heredado debe llamar a`super()`.De lo contrario,`"this"`no se "definirá".

 So here's the fix:
 Así que aquí está la solución:

 ```js run
 class Rabbit extends Object {
  constructor(name) {
 *!*
    super(); //need to call the parentconstructorwhen inheriting
    super(); //necesita llamar alconstructorpadre al heredar
 */!*
    this.name = name;
  }
 }

 let rabbit = new Rabbit("Rab");

 alert( rabbit.hasOwnProperty('name') ); //true
 alert( rabbit.hasOwnProperty('name') ); //verdadero
 ```

 But that's not all yet.
 Pero eso no es todo aún.

 Even after the fix, there's still important difference in`"class Rabbit extendsObject"` versus `class Rabbit`.
 Incluso después de la solución, todavía hay una diferencia importante en`"class Rabbit extendsObjetc"` versus `class Rabbit`.

 As we know, the"extends"syntax sets up two prototypes:
 Como sabemos, la sintaxis"extends"configura dos prototipos:

 1.Between`"prototype"`of the constructor functions (for methods).
 2.Between the constructor functions itself (for static methods).
 1.Entre el`"prototype"`de las funcionalidades del constructor (para métodos).
 2.Entre las funcionalidades propias del constructor (para métodos estáticos).

 In our case, for `class Rabbit extends Object`it means:
 En nuestro caso, para `class Rabbit extends Object`significa::

 ```js run
 class Rabbit extends Object {}

 alert( Rabbit.prototype.__proto__ === Object.prototype ); // (1)true
 alert( Rabbit.__proto__ === Object ); // (2)true
 alert( Rabbit.prototype.__proto__ === Object.prototype ); // (1)verdadero
 alert( Rabbit.__proto__ === Object ); // (2)verdadero
 ```

 So `Rabbit`now provides access to static methods of `Object`via`Rabbit`,like this:
 Entonces `Rabbit`ahora proporciona acceso a métodos estáticos de `Object`a través de`Rabbit`,como esto:

 ```js run
 class Rabbit extends Object {}

 *!*
 //normally we call Object.getOwnPropertyNames
 //normalmente llamamos Object.getOwnPropertyNames
 alert ( Rabbit.getOwnPropertyNames({a: 1, b: 2})); // a,b
 */!*
 ```

 But if we don't have `extends Object`, then `Rabbit.__proto__` is not set to `Object`.
 Pero si no tenemos `extend Object', entonces `Rabbit.__ proto__` no está configurado como `Object`.

 Here's the demo:
 Aqui la demostración:

 ```js run
 class Rabbit {}

 alert( Rabbit.prototype.__proto__ === Object.prototype ); // (1)true
 alert( Rabbit.__proto__ === Object ); // (2)false (!)
 alert( Rabbit.__proto__ === Function.prototype ); //as any function by default
 alert( Rabbit.prototype.__proto__ === Object.prototype ); // (1)verdadero
 alert( Rabbit.__proto__ === Object ); // (2)falso (!)
 alert( Rabbit.__proto__ === Function.prototype ); //como cualquier función por defecto

 *!*
 // error, nosuch function in Rabbit
 // error, nohay tal función en Rabbit
 alert ( Rabbit.getOwnPropertyNames({a: 1, b: 2})); // Error
 */!*
 ```

 So `Rabbit`doesn't provide access to static methods of `Object` in that case.
 Entonces `Rabbit`no proporciona acceso a métodos estáticos de 'Objeto' en ese caso.

 By the way, `Function.prototype`has "generic" function methods, like `call`, `bind` etc.They are ultimately available in both cases, because for the built-in`Object` constructor, `Object.__proto__ === Function.prototype`.
 Por cierto, `Function.prototype`tiene métodos de función "genéricos", como `call`, `bind` etc.En última instancia, están disponibles en ambos casos, porque para el constructor incorporado`Object`, `Object.__ proto__ === Function.prototype`.

 Here's the picture:
 Aqui está el gráfico:

 ![](rabbit-extends-object.svg)

 So, to put it short, there are two differences:
 Entonces, para resumir, hay dos diferencias:

 | class Rabbit | class Rabbit extends Object  |
 |--------------|------------------------------|
 | --             |needs to call `super()`in constructor |
 | --             |necesita llamar a `super()`en el constructor |
 | `Rabbit.__proto__ === Function.prototype` | `Rabbit.__proto__ === Object` |
diff --git a/1-js/09-classes/02-class-inheritance/3-class-extend-object/task.md b/1-js/09-classes/02-class-inheritance/3-class-extend-object/task.md
 importance:5
 importance:3

 ---

 #Class extends Object?
 #Clase extiende objeto?

 As we know, all objects normally inherit from`Object.prototype`and get access to "generic" object methods like`hasOwnProperty` etc.
 Como sabemos, todos los objetos normalmente heredan de`Object.prototype`y obtienen acceso a métodos de objetos "genéricos" como`hasOwnProperty`, etc..

 For instance:
 Por ejemplo:

 ```js run
 class Rabbit {
 let rabbit = new Rabbit("Rab");

 *!*
 // hasOwnProperty method is from Object.prototype
 // rabbit.__proto__ === Object.prototype
 alert( rabbit.hasOwnProperty('name') ); // true
 // el método hasOwnProperty es de Object.prototype
 alert( rabbit.hasOwnProperty('name') ); // verdadero
 */!*
 ```

 But if we spell it out explicitly like `"class Rabbit extendsObject"`,then the result would be different from a simple `"class Rabbit"`?
 Pero si lo deletreamos explícitamente como `"clase Rabbit extendsObjetc"`,entonces ¿el resultado sería diferente de un simple `"class Rabbit"`?

 What's the difference?
 ¿Cual es la diferencia?

 Here's an example of such code (it doesn't work -- why? fix it?):
 Aquí hay un ejemplo de dicho código (no funciona, ¿por qué? ¿Solucionarlo?):

 ```js
 class Rabbit extends Object {

 let rabbit = new Rabbit("Rab");

 alert( rabbit.hasOwnProperty('name') ); //true
 alert( rabbit.hasOwnProperty('name') ); //Error
 ```
Original file line number	Diff line number	Diff line change
		@@ -1,6 +1,6 @@
		That's because the child constructormust call `super()`.
		Eso es porque el constructorhijo debe llamar a `super()`.

		Here's the corrected code:
		Aqui está el código corregido:

		```js run
		class Animal {
Expand All		@@ -21,7 +21,7 @@ class Rabbit extends Animal {
		}

		!
		let rabbit = new Rabbit("White Rabbit"); //ok now
		let rabbit = new Rabbit("Conejo Blanco"); //bueno ahora
		/!
		alert(rabbit.name); //White Rabbit
		alert(rabbit.name); //Conejo Blanco
		```
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2,11 +2,11 @@ importance: 5

		---

		# Errorcreating an instance
		# Erroral crear una instancia

		Here's the code with`Rabbit`extending`Animal`.
		Aquí está el código de la clase`Rabbit`que extiende a`Animal`.

		Unfortunately,`Rabbit`objects can't be created. What's wrong? Fix it.
		Desafortunadamente, los objetos`Rabbit`no se pueden crear. ¿Que pasa? Arréglalo.
		```js run
		class Animal {

Expand All		@@ -24,7 +24,7 @@ class Rabbit extends Animal {
		}

		!
		let rabbit = new Rabbit("White Rabbit"); // Error:this is not defined
		let rabbit = new Rabbit("Conejo Blanco"); // Error:esto no está definido
		/!
		alert(rabbit.name);
		```
Original file line number	Diff line number	Diff line change
		@@ -1,7 +1,7 @@
		class ExtendedClock extends Clock {
		constructor(options) {
		super(options);
		let { precision=1000 } = options;
		let { precision =1000 } = options;
		this.precision = precision;
		}

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -7,7 +7,7 @@
		clock.start();


		/Your class should work like this: /
		/Tu clase debería funcionar así: /

		/*

Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2,14 +2,14 @@ importance: 5

		---

		#Extended clock
		#Reloj extendido

		We've got a `Clock` class. As of now, it prints the time every second.
		Tenemos una clase de 'Clock'. A partir de ahora, imprime la hora cada segundo.


		[js src="source.view/clock.js"]

		Create a new class `ExtendedClock`that inherits from `Clock`and adds the parameter `precision` -- the number of `ms` between "ticks".Should be `1000` (1second) by default.
		Crea una nueva clase `ExtendedClock`que herede de `Clock`y agrega el parámetro `precision`: este es el número de `milisegundos` entre "tics".Debe ser `1000` (1segundo) por defecto.

		-Your code should be in the file `extended-clock.js`
		-Don't modify the original`clock.js`. Extend it.
		-Tu código debe estar en el archivo `extended-clock.js`
		-No modifiques el`clock.js` original. Extiéndelo.
Original file line number	Diff line number	Diff line change
		@@ -1,81 +1,81 @@
		First, let's see why the latter code doesn't work.
		Primero, veamos por qué el último código no funciona.

		The reason becomes obvious if we try to run it. An inheriting class constructor must call`super()`.Otherwise`"this"`won't be "defined".
		La razón se vuelve obvia si tratamos de ejecutarlo. Un constructor de clase heredado debe llamar a`super()`.De lo contrario,`"this"`no se "definirá".

		So here's the fix:
		Así que aquí está la solución:

		```js run
		class Rabbit extends Object {
		constructor(name) {
		!
		super(); //need to call the parentconstructorwhen inheriting
		super(); //necesita llamar alconstructorpadre al heredar
		/!
		this.name = name;
		}
		}

		let rabbit = new Rabbit("Rab");

		alert( rabbit.hasOwnProperty('name') ); //true
		alert( rabbit.hasOwnProperty('name') ); //verdadero
		```

		But that's not all yet.
		Pero eso no es todo aún.

		Even after the fix, there's still important difference in`"class Rabbit extendsObject"` versus `class Rabbit`.
		Incluso después de la solución, todavía hay una diferencia importante en`"class Rabbit extendsObjetc"` versus `class Rabbit`.

		As we know, the"extends"syntax sets up two prototypes:
		Como sabemos, la sintaxis"extends"configura dos prototipos:

		1.Between`"prototype"`of the constructor functions (for methods).
		2.Between the constructor functions itself (for static methods).
		1.Entre el`"prototype"`de las funcionalidades del constructor (para métodos).
		2.Entre las funcionalidades propias del constructor (para métodos estáticos).

		In our case, for `class Rabbit extends Object`it means:
		En nuestro caso, para `class Rabbit extends Object`significa::

		```js run
		class Rabbit extends Object {}

		alert( Rabbit.prototype.__proto__ === Object.prototype ); // (1)true
		alert( Rabbit.__proto__ === Object ); // (2)true
		alert( Rabbit.prototype.__proto__ === Object.prototype ); // (1)verdadero
		alert( Rabbit.__proto__ === Object ); // (2)verdadero
		```

		So `Rabbit`now provides access to static methods of `Object`via`Rabbit`,like this:
		Entonces `Rabbit`ahora proporciona acceso a métodos estáticos de `Object`a través de`Rabbit`,como esto:

		```js run
		class Rabbit extends Object {}

		!
		//normally we call Object.getOwnPropertyNames
		//normalmente llamamos Object.getOwnPropertyNames
		alert ( Rabbit.getOwnPropertyNames({a: 1, b: 2})); // a,b
		/!
		```

		But if we don't have `extends Object`, then `Rabbit.__proto__` is not set to `Object`.
		Pero si no tenemos `extend Object', entonces `Rabbit.__ proto__` no está configurado como `Object`.

		Here's the demo:
		Aqui la demostración:

		```js run
		class Rabbit {}

		alert( Rabbit.prototype.__proto__ === Object.prototype ); // (1)true
		alert( Rabbit.__proto__ === Object ); // (2)false (!)
		alert( Rabbit.__proto__ === Function.prototype ); //as any function by default
		alert( Rabbit.prototype.__proto__ === Object.prototype ); // (1)verdadero
		alert( Rabbit.__proto__ === Object ); // (2)falso (!)
		alert( Rabbit.__proto__ === Function.prototype ); //como cualquier función por defecto

		!
		// error, nosuch function in Rabbit
		// error, nohay tal función en Rabbit
		alert ( Rabbit.getOwnPropertyNames({a: 1, b: 2})); // Error
		/!
		```

		So `Rabbit`doesn't provide access to static methods of `Object` in that case.
		Entonces `Rabbit`no proporciona acceso a métodos estáticos de 'Objeto' en ese caso.

		By the way, `Function.prototype`has "generic" function methods, like `call`, `bind` etc.They are ultimately available in both cases, because for the built-in`Object` constructor, `Object.__proto__ === Function.prototype`.
		Por cierto, `Function.prototype`tiene métodos de función "genéricos", como `call`, `bind` etc.En última instancia, están disponibles en ambos casos, porque para el constructor incorporado`Object`, `Object.__ proto__ === Function.prototype`.

		Here's the picture:
		Aqui está el gráfico:

		![](rabbit-extends-object.svg)

		So, to put it short, there are two differences:
		Entonces, para resumir, hay dos diferencias:

		\| class Rabbit \| class Rabbit extends Object \|
		\|--------------\|------------------------------\|
		\| -- \|needs to call `super()`in constructor \|
		\| -- \|necesita llamar a `super()`en el constructor \|
		\| `Rabbit.__proto__ === Function.prototype` \| `Rabbit.__proto__ === Object` \|
Original file line number	Diff line number	Diff line change
		@@ -1,12 +1,12 @@
		importance:5
		importance:3

		---

		#Class extends Object?
		#Clase extiende objeto?

		As we know, all objects normally inherit from`Object.prototype`and get access to "generic" object methods like`hasOwnProperty` etc.
		Como sabemos, todos los objetos normalmente heredan de`Object.prototype`y obtienen acceso a métodos de objetos "genéricos" como`hasOwnProperty`, etc..

		For instance:
		Por ejemplo:

		```js run
		class Rabbit {
Expand All		@@ -18,17 +18,16 @@ class Rabbit {
		let rabbit = new Rabbit("Rab");

		!
		// hasOwnProperty method is from Object.prototype
		// rabbit.__proto__ === Object.prototype
		alert( rabbit.hasOwnProperty('name') ); // true
		// el método hasOwnProperty es de Object.prototype
		alert( rabbit.hasOwnProperty('name') ); // verdadero
		/!
		```

		But if we spell it out explicitly like `"class Rabbit extendsObject"`,then the result would be different from a simple `"class Rabbit"`?
		Pero si lo deletreamos explícitamente como `"clase Rabbit extendsObjetc"`,entonces ¿el resultado sería diferente de un simple `"class Rabbit"`?

		What's the difference?
		¿Cual es la diferencia?

		Here's an example of such code (it doesn't work -- why? fix it?):
		Aquí hay un ejemplo de dicho código (no funciona, ¿por qué? ¿Solucionarlo?):

		```js
		class Rabbit extends Object {
Expand All		@@ -39,5 +38,5 @@ class Rabbit extends Object {

		let rabbit = new Rabbit("Rab");

		alert( rabbit.hasOwnProperty('name') ); //true
		alert( rabbit.hasOwnProperty('name') ); //Error
		```