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JavaScript Object-Oriented JavaScript (2015) Constructor Functions and Prototypes Making the UI Work

Nikola Jankovic
Nikola Jankovic
10,793 Points

The console display "this.songs[i].toHTML is not a functio"???

this is my code playlist.js

function Playlist() {
    this.songs= [];
    this.nowPlayingIndex= 0;

Playlist.prototype.add = function() {

Playlist.prototype.play = function() {
    var currentSong= this.songs[nowPlayingIndex];

Playlist.prototype.stop = function(){
    var currentSong= this.songs(nowPlayingIndex);

Playlist.prototype.next = function() {
    if(this.nowPlayingIndex=== this.songs.length){
        this.nowPlayingIndex= 0;

Playlist.prototype.renderInElement = function(list) {
    list.innerHTML= "";
    for(var i= 0; i< this.songs.length; i++){
        list.innerHTML+= this.songs[i].toHTML();

, add.js

var playlist= new Playlist();

var hereComesTheSun= new Song('Here Comes The Sun', 'Beatles', '2:54');
var walkingOnSunshine= new Song('Walking On Sunshine', 'Katrina and the Waves', '3:43');


var playlistElement= document.getElementById("playlist");


, song.js

function Song(title, artist, duration) {
    this.title= title;
    this.artist= artist;
    this.duration= duration;
    this.isPlaying= false;

Song.prototype.play = function() {
    this.isPlaying= true;

Song.prototype.stop = function() {
    this.isPlaying= false;

Song.prototype.toHTML = function() {
    var htmlString= '<li ';
    htmlString+= 'class="current"';
    htmlString+= '>';
    htmlString+= this.title;
    htmlString+= ' - ';
    htmlString+= '<span calss="duration">'
    htmlString+= this.duration;
    htmlString+= '</span></li>';

    return htmlString;

When I run the code it wont show songs and in the console it display error "this.songs[i].toHTML is not a functio". Can someone help????

1 Answer

I quickly looked at your code, I am not 100% sure but I believe you need to call the function without the (), like this:

list.innerHTML+= this.songs[i].toHTML;

Please try this simple change and let us know the result, cheers.

Nikola Jankovic
Nikola Jankovic
10,793 Points

Yes that was the problem, thank's.