typescript - Casting HTMLElement to HTMLAudioElement -

i have line of typescript:

var audio: htmlaudioelement = document.getelementbyid("audioelement"); 

however, build error:

type htmlelement not assignable type 'htmlaudioelement'. 

is there different way should retrieving element htmlaudioelement, or cast htmlaudioelement?

the casting sutras typescript looks this:

var audio = <htmlaudioelement>document.getelementbyid("audioelement"); 

and can either specify type on audio variable if want, typescript pick automatically you.