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

libjs-codemirror is installed in your system.

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

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

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

libjs-codemirror package basic information: