npm does not support Node.js v10

[Fred]

$ npm
npm WARN npm npm does not support Node.js v10.15.2
npm WARN npm You should probably upgrade to a newer version of node as we
npm WARN npm can't make any promises that npm will work with this version.
npm WARN npm Supported releases of Node.js are the latest release of 4, 6, 7, 8, 9.
npm WARN npm You can find the latest version at https://nodejs.org/

Upgrade npm to version 6.9.0.

ProblemType: Bug
DistroRelease: Ubuntu 19.04
Package: npm 5.8.0+ds6-4
ProcVersionSignature: Ubuntu 5.0.0-7.8-generic 5.0.0
Uname: Linux 5.0.0-7-generic x86_64
ApportVersion: 2.20.10-0ubuntu23
Architecture: amd64
CurrentDesktop: GNOME
Date: Sun Mar 24 00:15:02 2019
InstallationDate: Installed on 2013-12-26 (1912 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
PackageArchitecture: all
SourcePackage: npm
UpgradeStatus: No upgrade log present (probably fresh install)