Https://www.codecademy.com/paths/web-development/tracks/webdev-intermediate-javascript/modules/learn-javascript-classes/projects/build-a-library


#1

https://www.codecademy.com/paths/web-development/tracks/webdev-intermediate-javascript/modules/learn-javascript-classes/projects/build-a-library

Hello!
I do not know why I keep getting a syntax error from 'super" keyword, from subclasses Book and Movies. Located on first line of every Constructor. Anyone guess ??

//parent class Media
//tittle the only property in commun with 3 sub classes that doesn t have a default value.
class Media {
Constructor(title) {
this._tittle = title;
this._isCheckedOut = false;
this._ratings = ;
}
get tittle() {
return this._title;
}
//isCheckedOut needs a “value”, as we need to assign something to this.
get isCheckedOut() {
return this._isCheckedOut;
}
get ratings() {
return this._ratings;
}
toggleCheckOutStatus() {
this._isCheckedOut = !this._isCheckedOut;
}
getAverageRating() {
let ratingsSum =
this.ratings.reduce((currentSum, rating) =>
currentSum + rating, 0);
return ratingsSum / this._ratings.length;
}

addRating(value) {
this.ratings.push(value)
}

set isCheckedOut(value) {
this._isCheckedOut = value;
}
}
//Sub class Book (exentintion of parent class Media)
//Author, title and pages are 3 properties within Book, therefore go as arguments for constructor.
class Book extends Media {
Constructor(author, title, pages) {
super(title);
this._author = author;
this._pages = 0;
}

get author() {
return this._author;
}
get pages() {
return this._pages;
}
}

class Movie extends Media {
Constructor(director, title, runTime) {
super(title);
this._director = director;
this._runtime = 0;
}

get director() {
return this._director;
}
get runTime() {
return this._runTime;
}
}
const historyOfEverything = new Book(‘Bill Bryson’, ‘A Short History of Nearly Everything’, 544);
historyOfEverything.toggleCheckOutStatus();
console.log(historyOfEveryThing.isCheckedOut());
historyOfEverything.addRating(4);
historyOfEverything.addRating(5);
historyOfEverything.addRating(5);
console.log(historyOfEverything.getAverageRating());

const speed = new Movie(‘Jan de Bont’, ‘Speed’, 116);
speed.toggleCheckOutStatus();
console.log(speed.isCheckedOut());
speed.addRating(1);
speed.addRating(1);
speed.addRating(5);
console.log(speed.getAverageRating());


#2

Keywords are not to be capitalized, only the class name is written thus.

constructor(author, title, pages)

#3

Thank you!
By the way, now there is now an error with .push(), on parent class media. What s wrong ?

addRating(value) {
this.ratings.push(value);
}


#4

Push it onto the backing variable, not the get() variable.

this._ratings.push(value);

#5

I am afraid I do not follow you. What do you mean by backing variable ?
The video shows ‘this.ratings.push(value);’, without underline.

updated code below:

//parent class Media
//tittle the only property in commun with 3 sub classes that doesn t have a default value.
class Media {
  Constructor(title) {
    this._tittle = title;
    this._isCheckedOut = false;
    this._ratings = [];
  }
  get title() {
    return this._title;
  }
  //isCheckedOut needs a "value", as we need to assign something to this.
  get isCheckedOut() {
    return this._isCheckedOut;
  }
  get ratings() {
    return this._ratings;
  }
  toggleCheckOutStatus() {
    this._isCheckedOut = !this._isCheckedOut;
  }
  
   set isCheckedOut(value) {
    this._isCheckedOut = value;
  }
  
  getAverageRating() {
    let ratingsSum = 
    this.ratings.reduce((currentSum, rating) => 
    currentSum + rating, 0);
        return ratingsSum / this._ratings.length;
  }
    
    addRating(value) {
    this.ratings.push(value);
  }
}
//Sub class Book (exentintion of parent class Media)
//Author, title and pages are 3 properties within Book, therefore go as arguments for constructor. 
class Book extends Media {
  constructor(author, title, pages) {
    super(title);
    this._author = author;
    this._pages = pages;
  }
  
   get author() {
    return this._author;
  }
  get pages() {
    return this._pages;
  }  
}

class Movie extends Media {
  constructor(director, title, runTime) {
    super(title);
    this._director = director;
    this._runtime = 0;
  }
  
   get director() {
    return this._director;
  }
  get runTime() {
    return this._runTime;
  }  
}
const historyOfEverything = new Book('Bill Bryson', 'A Short History of Nearly Everything', 544);
historyOfEverything.toggleCheckOutStatus();
console.log(historyOfEverything.isCheckedOut);
historyOfEverything.addRating(4);
historyOfEverything.addRating(5);
historyOfEverything.addRating(5);
console.log(historyOfEverything.getAverageRating());

const speed = new Movie('Jan de Bont', 'Speed', 116);
speed.toggleCheckOutStatus();
console.log(speed.isCheckedOut());
speed.addRating(1);
speed.addRating(1);
speed.addRating(5);
console.log(speed.getAverageRating());

#6

Did you try the way I showed in the example?


#7

More typos. constructor and _title.


#8

I gotcha!!! Finally, the code up and running just fine. Tks a lot!

script.js
class Media {
  constructor(title) {
    this._title = title;
    this._isCheckedOut = false;
    this._ratings = [];
  }
  get title() {
    return this._title;
  }
  //isCheckedOut needs a "value", as we need to assign something to this.
  get isCheckedOut() {
    return this._isCheckedOut;
  }
  get ratings() {
    return this._ratings;
  }
  toggleCheckOutStatus() {
    this._isCheckedOut = !this._isCheckedOut;
  }
  
   set isCheckedOut(value) {
    this._isCheckedOut = value;
  }
  
  getAverageRating() {
    let ratingsSum = 
    this.ratings.reduce((currentSum, rating) => 
    currentSum + rating, 0);
        return ratingsSum / this._ratings.length;
  }
    
    addRating(value) {
    this.ratings.push(value);
  }
}
//Sub class Book (exentintion of parent class Media)
//Author, title and pages are 3 properties within Book, therefore go as arguments for constructor. 
class Book extends Media {
  constructor(author, title, pages) {
    super(title);
    this._author = author;
    this._pages = pages;
  }
  
   get author() {
    return this._author;
  }
  get pages() {
    return this._pages;
  }  
}

class Movie extends Media {
  constructor(director, title, runTime) {
    super(title);
    this._director = director;
    this._runtime = 0;
  }
  
   get director() {
    return this._director;
  }
  get runTime() {
    return this._runTime;
  }  
}
const historyOfEverything = new Book('Bill Bryson', 'A Short History of Nearly Everything', 544);
historyOfEverything.toggleCheckOutStatus();
console.log(historyOfEverything.isCheckedOut);
historyOfEverything.addRating(4);
historyOfEverything.addRating(5);
historyOfEverything.addRating(5);
console.log(historyOfEverything.getAverageRating());

const speed = new Movie('Jan de Bont', 'Speed', 116);
speed.toggleCheckOutStatus();
console.log(speed.isCheckedOut);
speed.addRating(1);
speed.addRating(1);
speed.addRating(5);
console.log(speed.getAverageRating());