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

David Curran
David Curran
7,682 Points
Posted by David Curran
David Curran
7,682 Points

DOT syntax

I am a little confused with some of the coding concepts in this chapter of OOP. Why does Andrew do the following?

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

The this.nowPlayingIndex is the index of the array songs. Therefore variable currentSong will then hold the properties title, artist and duration of that index element. But why write currentSong.play(); and not playlist.play();

1 Answer

Steven Parker
Steven Parker
229,732 Points
Steven Parker
Steven Parker
229,732 Points

The purpose of curentSong.play() is to begin playing a song.

There are two different methods in this project named play. The one being defined here is for a Playlist object, which will then call the play method on a Song object. And currentSong is a Song object that was chosen from the list of songs using nowPlayingIndex.

Calling playlist.play() here would be an improper reference to the global playlist, and would also cause an infinite recursion loop, since it is that method which is being defined here.