安装 Node.js 和 NPM 在 windows10 subsystem

You can install Node.js and NPM with your Windows PowerShell as well, so if you've done that it won't work properly for your Subsystem. That means you have to install it twice (Powershell and Subsystem) or decide on one thing.

If the preceding text, has not helped you, this is how to solve the problem:
Remove your current installations

sudo apt-get --purge remove node
("sudo apt autoremove node" if console is asking for it)
sudo apt-get --purge remove nodejs

Install node the right way. This is for version 14 (view current LTS version):

curl -fsSL https://deb.nodesource.com/setup_14.x | sudo -E bash -
sudo apt-get install -y nodejs

Then install build tools so you can install add-ons for npm later

重启 subsystem

Now you can type in

npm -v
node -v
Same thing: nodejs -v

to check whether Node.js and NPM are installed correctly. If it shows nothing, restart the shell.

Here are two links that may also help you.
https://nodejs.org/en/download/package-manager/#debian-and-ubuntu-based-linux-distributions https://github.com/nodesource/distributions/blob/master/README.md#debinstall

Also, take a look at the Node Version Manager (NVM). With it, you can easily switch back and forth between versions.