Nrthugu

I am learning on Angular JS. I have install the Node and NPM. But I am getting the following error.

if I run the following command as my username then it shows me the version

npm -v
5.6.0

But if I run the command as a Root user then the following message I am getting

npm -v

Command 'npm' is available in '/snap/bin/npm'

The command could not be located because '/snap/bin' is not included in the PATH environment variable.

npm: command not found

I am also getting the Error for the following command as root user---

apt-get install npm

Reading package lists... Done

Building dependency tree

Reading state information... Done

Some packages could not be installed. This may mean that you have

requested an impossible situation or if you are using the unstable

distribution that some required packages have not yet been created

or been moved out of Incoming.

The following information may help to resolve the situation:

The following packages have unmet dependencies:

npm : Depends: node-gyp (>= 0.10.9) but it is not going to be installed

E: Unable to correct problems, you have held broken packages.

My Question is

1) What is the root cause of this issue.
2) How can I solve this issue?

I am using Ubuntu 18.04.1 LTS