$ sudo apt-get update
$ sudo apt-get install libjs-mediaelement 

libjs-mediaelement is installed in your system.

Make ensure the libjs-mediaelement package were installed using the commands given below,

$ sudo dpkg-query -l | grep libjs-mediaelement *

You will get with libjs-mediaelement package name, version, architecture and description in a table

libjs-mediaelement package basic information: