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JavaScript

Posted by brandonlind2
brandonlind2
7,823 Points

Why does media.call() need more arguments then 'this'?

I'm a bit confused as to way media.call, needs the arguments of the inherited constructor function, wouldn't the arguments of the constructor that is inheriting be used? I understand way the 'this' argument is needed in media.call but I don't understand why title and duration is needed.

I'm trying to understand how the code works, I'm having trouble seeing the value of he arguments of the inherited constructor function other the 'this', why wouldnt this this work?

function song (title, artist, duration){ media.call(this); this.artist= artist; }

1 Answer

Balázs Buri
Balázs Buri
8,799 Points

in your code:

function Song(title, artist, duration) { //title and duration parameters unused inside this function
    Media.call(this);
    this.artist = artist;
}

you create the class Song (you should capitalize class names) which will extend the Media class. You don't use the title and duration parameters anywhere inside your function however so they are lost forever. Those parameters aren't passed automatically to the parent Media. In the correct code:

function Song(title, artist, duration) {
    Media.call(this, title, duration); 
    this.artist = artist;
}

the parameters are passed to Media. But because this is now the song, inside Media:

this.title = title; will mean song.title = title

also it's the only place where the parameter is finally stored.

hope this helps