NodeSource provides binary distributions of Node.js; complete installation instructions can be found here. The instructions have been copied below for your reference. Instructions are the same for updating to the latest version.

Run once:

sudo apt-get update
sudo apt-get install -y ca-certificates curl gnupg
sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://deb.nodesource.com/gpgkey/nodesource-repo.gpg.key | sudo gpg --dearmor -o /etc/apt/keyrings/nodesource.gpg

Run whenever you want to change the major version of Node.js:

NODE_MAJOR=20
echo "deb [signed-by=/etc/apt/keyrings/nodesource.gpg] https://deb.nodesource.com/node_$NODE_MAJOR.x nodistro main" | sudo tee /etc/apt/sources.list.d/nodesource.list
sudo apt-get update
sudo apt-get install nodejs -y

Prior to August 2023: Previously versions of this answer involved the use of a series of setup_XX.x scripts that you'd run to install/update Node.js:

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

But as @eis pointed out, these scripts are no longer supported. To see the previous answers, please look at the edit history for this answer.

According to official docs to install node on Debian and Ubuntu based distributions:

node v12 (Old)

curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash -
sudo apt-get install -y nodejs

node v14 (For new users: install this one):

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

node v15 (Current version):

curl -sL https://deb.nodesource.com/setup_15.x | sudo -E bash -
sudo apt-get install -y nodejs

Other older versions: Just replace the desired version number in the link above.

Optional: install build tools

To compile and install native packages

sudo apt-get install -y build-essential

To update node to the latest version just:

sudo apt update
sudo apt upgrade

To keep npm updated

sudo npm i -g npm

To find out other versions try npm info npm and in versions find your desired version and replace [version-tag] with that version tag in npm i -g npm@[version-tag]

And I also recommend trying yarn instead of npm

Install nodejs v20 on Debian and Ubuntu based distributions

step 1 : Download and import the Nodesource GPG key

sudo apt-get update
sudo apt-get install -y ca-certificates curl gnupg
sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://deb.nodesource.com/gpgkey/nodesource-repo.gpg.key | sudo gpg --dearmor -o /etc/apt/keyrings/nodesource.gpg

step 2 : Create deb repository

NODE_MAJOR=20
echo "deb [signed-by=/etc/apt/keyrings/nodesource.gpg] https://deb.nodesource.com/node_$NODE_MAJOR.x nodistro main" | sudo tee /etc/apt/sources.list.d/nodesource.list

optional: here we are installing nodejs v20 but if you want to install v18 change NODE_MAJOR=18 in above command. Similarly if you want to install nodejs v16 then change NODE_MAJOR=16.

step 3 : Run Update and Install

sudo apt-get update
sudo apt-get install nodejs -y

congratulations you just installed nodejs

To uninstall nodejs

sudo apt-get purge nodejs &&\
rm -r /etc/apt/sources.list.d/nodesource.list &&\
rm -r /etc/apt/keyrings/nodesource.gpg

Update for 2024

Since this question was posted, version 20 became the newest LTS version. So Ahmed Boutaraa's answer was correct for the version 14 part of the question, but people stumbling on this question may be seeking the most recent LTS. If you follow those instructions, you will be stuck in version 14.

Luckily, NodeSource also provides an installation script that installs the current LTS rather than a specific version. That should make this answer a bit more future-proof. You can also get the same info straight from the source.

As an aside, there is a script called nvm that is great for managing your node version. It makes it easy to install multiple versions, like if you work with multiple projects with different version requirements or if you want to experiment with the latest version and easily switch back to LTS for regular work. You can find installation instructions on their repository.

How to install the latest LTS version

This set of instructions will install whatever version is the latest LTS version. When a new version is released, you may have to run these instructions again to pull the new install script for the new version.

# As a user with sudo
curl -fsSL https://deb.nodesource.com/setup_lts.x | sudo -E bash -
sudo apt-get install -y nodejs

# OR as root
curl -fsSL https://deb.nodesource.com/setup_lts.x | bash -
apt-get install -y nodejs

How to install the latest non-LTS version

This set of instructions will install whatever version is the latest non-LTS version. When a new version is released, you may have to run these instructions again to pull the new install script for the new version.

# As a user with sudo
curl -fsSL https://deb.nodesource.com/setup_current.x | sudo -E bash -
sudo apt-get install -y nodejs

# OR as root
curl -fsSL https://deb.nodesource.com/setup_current.x | bash -
apt-get install -y nodejs

How to lock into v21 (latest, for now)

# As a user with sudo
curl -fsSL https://deb.nodesource.com/setup_21.x | sudo -E bash -
sudo apt-get install -y nodejs

# OR as root
curl -fsSL https://deb.nodesource.com/setup_21.x | bash -
apt-get install -y nodejs

How to lock into v20 (current LST)

# As a user with sudo
curl -fsSL https://deb.nodesource.com/setup_20.x | sudo -E bash -
sudo apt-get install -y nodejs

# OR as root
curl -fsSL https://deb.nodesource.com/setup_20.x | bash -
apt-get install -y nodejs

sudo npm install -g --force node@latest

Use that command, and it will fix your problem. The only issue with that is it will rewrite your node folder.