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Node.js

Node.js runs JavaScript outside the browser. See also PM2 for running Node apps in production and Jest for testing.

Install​

nvm​

nvm lets you install and switch between node versions from the command line.

# Install
NVM_VER=v0.40.4
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/$NVM_VER/install.sh | bash

wget -qO- https://raw.githubusercontent.com/nvm-sh/nvm/$NVM_VER/install.sh | bash

source ~/.bashrc
nvm --version

# If ~/.bash_profile exists, source ~/.bashrc from it:
#   if [ -f ~/.bashrc ]; then
#     . ~/.bashrc
#   fi

# List remote LTS versions only
nvm ls-remote --lts

# Choose a version
NODE_VER=v24.16.0

# Install / use it
nvm install $NODE_VER
nvm use $NODE_VER

# nvm keeps "forgetting" node in a new terminal session — set a default
nvm alias default $NODE_VER

# List installed versions
nvm ls

# Run a script with a specific version
nvm run $NODE_VER app.js

# Remove a version
nvm uninstall $NODE_VER

# Remove the current node binary
rm `which node`

# Upgrade nvm itself
(
  cd "$NVM_DIR"
  git fetch --tags origin
  git checkout `git describe --abbrev=0 --tags --match "v[0-9]*" $(git rev-list --tags --max-count=1)`
) && \. "$NVM_DIR/nvm.sh"

APT (Debian/Ubuntu)​

Install from NodeSource when you need a system-wide package.

# Current setup script (replace the version as needed)
curl -sL https://deb.nodesource.com/setup_10.x | sudo bash -
sudo apt-get install nodejs

# Pin an old series
apt install nodejs=0.10*

# Install an old 12.x directly
sudo curl -sL https://deb.nodesource.com/setup_12.x -o nodesource_setup.sh
sudo bash nodesource_setup.sh
sudo apt-get -y install nodejs

npm​

Use the npm bundled with the node LTS version.

# Reinstall / upgrade npm itself
npm install npm@latest -g

# Initialize a project
npm init

# Inspect config and the resolved node version
npm config list

# Funding info
npm audit fund
npm config set fund false   # turn it off

# Update globally-installed packages (no output means everything is current)
npm update -g
npm outdated -g

# List installed packages
npm list

# Remove packages not listed in package.json
npm prune

Linking node/npm/pm2 into /usr/bin​

When npm -v or pm2 -v work interactively but pm2 deploy reports command not found, expose the binaries system-wide:

sudo ln -s /root/.nvm/versions/node/v22.15.0/bin/npm  /usr/bin/npm
sudo ln -s /root/.nvm/versions/node/v22.15.0/bin/node /usr/bin/node
sudo ln -s /root/.nvm/versions/node/v22.15.0/bin/pm2  /usr/bin/pm2

# Or point them at whatever is currently active
sudo rm -f /usr/bin/npm /usr/bin/node /usr/bin/pm2
sudo ln -s $(which npm)  /usr/bin/
sudo ln -s $(which node) /usr/bin/
sudo ln -s $(which pm2)  /usr/bin/

# A symlink can break after updating/compiling/installing software (it shows up
# as red text in ls). Inspect and repair it:
readlink -v /usr/bin/npm
sudo ln -sfn /root/.nvm/versions/node/v22.15.0/bin/npm  /usr/bin/npm
sudo ln -sfn /root/.nvm/versions/node/v22.15.0/bin/node /usr/bin/node
sudo ln -sfn /root/.nvm/versions/node/v22.15.0/bin/pm2  /usr/bin/pm2

Updating packages​

npm install                       # install everything from package.json
npm install package_name --save   # add / upgrade a specific dependency
npm outdated                      # which modules are out of date
npm update                        # update to the wanted version
npm update --save                 # also bump the numbers in package.json
npm update -g                     # update global packages

# A short cheat sheet
npm list --depth 0                # top-level packages in this project
npm audit                         # which dependencies are vulnerable
npm update package_name           # update one already-installed package
npm uninstall package_name && npm install package_name@version  # pin a version
npm cache clean --force           # clear npm's package cache

Express​

npm install express --save

Generate a template project (the generator is deprecated but still handy):

npm install express-generator -g
express --view=pug project1
cd project1
npm install
vi bin/www        # change the port in normalizePort(process.env.PORT || '3000')
DEBUG=project1:* npm start
# Visit http://localhost:3000/

forever​

forever list
forever start dist/app.js
forever restart dist/app.js
forever stop 38282
forever stopall

Useful packages​

npm-check-updates​

Upgrade package.json version hints to the newest releases (including major versions) so npm can install them.

npm install -g npm-check-updates
ncu                            # show available updates
ncu --upgrade                  # ncu -u — write them to package.json
ncu --interactive              # ncu -i
ncu --interactive --format group

# Without installing globally
npx npm-check-updates
npx npm-check-updates -u

npkill​

Find and remove old, heavy node_modules folders.

npm install npkill -g
npx npkill
npx npkill -D -x
npx npkill --delete-all --directory C:\Temp

Mock Service Worker (MSW)​

npm install msw --save-dev

Jest​

jest --env=node        # run in a specific environment
npx jest --showConfig
npx jest --coverage

local-ssl-proxy​

npx local-ssl-proxy --key localhost+2-key.pem --cert localhost+2.pem --source 3001 --target 3000 --hostname localhost

Miscellaneous​

# Windows build tools
npm i -g windows-build-tools

# V8 stack size (default: 984 kB)
node --v8-options | grep -B0 -A1 stack-size

-D / --save-dev: the package appears in devDependencies.

Jest: "Cannot find module" with path aliases​

Jest does not support path aliases by default, so a test can fail with Cannot find module 'src/index' from 'index.js'. Add a mapping in jest.config.js:

const customJestConfig = {
  moduleNameMapper: { '@src(.*)$': '<rootDir>/src/$1' },
};

Concepts​

Relative URLs in Node.js​

You don't use them. In Node.js there is nothing for a URL to be relative to. When describing network behavior for a Node.js application, use the absolute URLs you are requesting. If you are using MSW with a Node.js-based test runner such as Jest or Vitest, configure the runner to support relative URLs (for example, by polyfilling the window.location object).