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JavaScript Object-Oriented JavaScript (2015) Constructor Functions and Prototypes Playlist Project

Posted by john larson
john larson
16,594 Points

Playlist.prototype.play & Song.prototype.play: They are interacting, I'm a little foggy how.

//both Playlist and Song have a .play()
//how does Playlist distinguish which .play() to use?

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

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

3 Answers

Steven Parker
Steven Parker
229,744 Points
Steven Parker
Steven Parker
229,744 Points

:point_right: The method used depends on the thing you use it on.

For example, say you have a Playlist named mylist, and a Song named mysong.

Now if you do this: mylist.play(); — it will use the play method that was defined for the Playlist prototype.

But if you do this: mysong.play(); — it will use the method defined for the Song prototype.

Does that clear it up?

john larson
john larson
16,594 Points

I have this vague idea of what you are saying. 1: are you saying it has to do with where it is called? ie: the thing you use it on? I hate to belabor this but, let me ask it this way. 

//How does Playlist.prototype.play
//know that currentSong.play();
// is not referring to itself?

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

I always appreciate your help. Thanks.

giseletoledo2
giseletoledo2
3,480 Points
giseletoledo2
giseletoledo2
3,480 Points

I don't know if this answer your question, but in the example of the dice was like that ( I don't know if the sintaxe it's right):

function Playlist() { this.songs = []; this.nowPlayingIndex = 0; this.currentSong = this.songs[this.nowPlayingIndex]; this.playSong = function() { this.currentSong.play(); }; }

Playlist.prototype.play it's part of Playlist, it's just outside the function.

john larson
john larson
16,594 Points

Gislel, I took a break from js cause it was starting to make my head hurt. I'll go back to it after I finish Python. Thank you for your response, I'll keep this as reference when I need it :D

function Playlist() { 
    this.songs = []; 
    this.nowPlayingIndex = 0; 
    this.currentSong = this.songs[this.nowPlayingIndex]; 
    this.playSong = function() { 
        this.currentSong.play(); 
    }; 
}
giseletoledo2
giseletoledo2
3,480 Points
giseletoledo2
giseletoledo2
3,480 Points

Ok, it's dificult too learn some things in Javascript.