Build a Library Project - JS

class Media {
constructor(title) {
this._title = title;
this._isCheckedOut = false;
this._ratings = ;
}

get title () {
return this._title;
}

get isCheckedOut(){
return this._isCheckedOut;
}

get ratings(){
return this._ratings;
}

set isCheckedOut(value) {
this._isCheckedOut = value;
}

toggleCheckOutStatus () {
this._isCheckedOut = !this._isCheckedOut
}

getAverageRating () {
let ratingsSum = this.ratings.reduce((currentSum, ratings) => accumulator + ratings, 0);
return ratingsSum / this._ratings.length
}

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

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(title, director, 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);

historyOfEverything.toggleCheckOutStatus()

console.log(historyOfEverything.isCheckedOut);

historyOfEverything.addRating(4, 5, 5);

console.log(historyOfEverything.getAverageRating());

Can someone pls explain why I’m not able to get an average rating pls - followed the steps and cant understand why its not working, really confused me lol.