Build a library inheritance issues

#1

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

I’m having troubles with the inheritance of the Media class by the Book class.

I believe I coded it right, then I watched the tutorial help video & it did the same as me. I also copied & pasted key variables to ensure that they were identical. it worked on the video, but not for me.

The trouble I’m having is that when the code tries to push a new value onto the end of the ratings array, the ratings array is undefined & so performing a push on undefined generates an error.

this.ratings.push(newRating);
^
TypeError: Cannot read property ‘push’ of undefined

ratings was defined in Media as such:
class Media {
constuctor(title) {
this._title = title;
this._ratings = ;
this._isCheckedOut = false;
}

get title() {
return this._title;
} …rest of the class }

Any help ? … Please!

#2

Please post your full code

did you implement a getter for _ratings property?

#3 
class Media {
  constuctor(title) {
    this._title = title;
    this._ratings = [];
    this._isCheckedOut = false;
  }

  get title() {
    return this._title;
  }

  get isCheckedOut() {
    return this._isCheckedOut;
  }
  
  get ratings() {
    return this._ratings;
  }
  
  set isCheckedOut(checkOutStatus) {
    this._isCheckedOut = checkOutStatus;
  }
  
  toggleChekOutStatus() {
    this._isCheckedOut = !this._isCheckedOut;
  }
  
  getAverageRating () {
    const reducer = (accumulator, currentValue) => accumulator + currentValue;
    let ratingsSum = this.ratings.reduce(reducer);
    let ratingsNum = this.ratings.length;
    return ratingsSum/ratingsNum;
  }
  
  addRating(newRating) {
    this.ratings.push(newRating);
  }
}

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 = runTime;
  }
  
  get director() {
    return this._director;
  }
  
  get runTime() {
    return this._runTime;
  }
}

const historyOfEverything  = new Book('Bill Bryson','A Short History of Nearly Everything', 544);
console.log(historyOfEverything);
historyOfEverything.toggleChekOutStatus();
console.log(historyOfEverything.isCheckedOut);
console.log(historyOfEverything.ratings);
console.log(historyOfEverything.title);

historyOfEverything.addRating(4);
historyOfEverything.addRating(5);
historyOfEverything.addRating(5);
console.log(historyOfEverything.getAverageRating());
#4

I implemented the getter for ratings however, the problem seems to be that the super() has not initiated the media constructor. The toggleChekOutStatus works (even though I spelt it wrong, but consistently wrong :slight_smile: , so the media class is understood by the Book class.

#5

seems you solved your own problem? Check the spelling of your Media constructor method

#6

A thousand thankyous.

#7

The important lesson is here, if you find an issue that a method (like constructor) isn’t called, you need to learn how to debug it