【Frontend Development Essential Tools Series】Part One：Mastering npm, nvm, and npx to Optimize Your Development Workflow

• Node.js package management tool used to install, manage, and share JavaScript packages.
• package.json: When you use $npm install, the project installs packages based on this file.
• package.lock.json: A feature introduced in npm 5.0 that can control the package versions that the project depends on.

Commonly used commands for npm install:

• -g or --globe: Global installation command, installs in your local environment, allowing you to use the installed package anywhere on your computer.
• --save or -S: Before npm 5.0, using $ npm install <package-name> would only install the package in the node_modules folder without changing package.json. After 5.0, package.json is automatically changed after installation, so this option is not used as often.
• --save--dev or -D: Only installs in the development environment, such as testing frameworks and code linting tools, which are not needed in the production environment.
• npm install --production: Executes the installation command. Only installs packages in the dependencies of package.json, ignoring packages in devDependencies, which helps reduce the burden on the production environment.

• In different projects, we may need to rely on different Node.js versions. You can use this tool to set different versions for each project.
• Can test project compatibility under different Node.js versions.
• When Node.js has a new version, you can use nvm to install and try the new version without worrying about affecting the stable version in your local environment.

nvm install <version>: Installs the specified version of Node.js. nvm use <version>: Switches to the specified version of Node.js. nvm alias default <version>: Sets the default Node.js version.

If I use nvm in a project, how does nvm know if I want to change the project’s Node.js version or the global Node.js version?

• nvm uses the .nvmrc file to manage the Node.js version under each project.
• The .nvmrc file is a simple text file that contains a Node.js version string, usually only one line.
• When you execute nvm use in the project root directory without specifying a version number, it will start looking for the .nvmrc file. It will automatically search for .nvmrc in the current directory and parent directories. If found, it can use the version specified in the file.
• If you execute nvm use in a project directory without an .nvmrc file, nvm will use the Node.js version you are using in your local environment.

• npx is an npm execution tool mainly used to manage the execution of npm packages. It has been available since npm 5.2.
• It can download a temporary version of a package in your project, which will be deleted after a single execution.
• npx does not change your package.json, so it can keep your environment uncontaminated.

• Where is the temporary download location? In the cache directory of the local environment. When you use $npx package@1.1.1 --version, it will first search for package@1.1.1 in the local node_modules/.bin. If this version is not found, it will search in the cache directory of the local environment, which is usually ~/.npm/_cacache on Mac. If still not found, it will temporarily download a new version from the npm server to your cache directory.

• Do I need to re-run the npx command after executing it once? Yes, after executing the program, npx will clean up the temporary directory. If you need to test version 1.1.1 again, you must re-execute $npm package@1.1.1 --version.