After executing "hash -r" nothing can be installed (my concern is installing npm and nodejs)

I want to install latest version of npm and nodejs. I need it to run angular js project. I installed npm using "sudo apt-get install npm". But it installed 1.3.0 something version which is not latest. I searched for how to remove npm (to install latest) on net and I found to do "hash -r" and further some process.

But when I executed this command, nothing could be installed. Even I cannot see the currently installed version by using "npm -v". This command shows nothing.

:(

What do the "hash -r" command do? How to undo it? How do I do now to install npm and nodejs on ubuntu?

Thanks in advance:)

via Vrushali Sabnis