How to install specified directory using npm in Node.js

While using Node.js, normally package installation is done through npm (Node Package Manager) from a registry or from an actual local file system path. Sometimes, instead of installing a package from npm registry, you may want to install a package from a directory, which is already there in your system. It is helpful in cases where you want to test packages locally before deploying them or when using local dependencies.

Syntax:

It has the following syntax:

• <path_to_directory>: The relative or absolute path to the directory where the package is located.

Parameters:

• path_to_directory: It is the local directory path to where the package that you want to install is found. It can be either:
  
  1. An absolute path (/home/user/project on Linux or C: For compiling the java programs between local drives arranged in a network (for example, through drive R: of this PC or D:\Users\user\project on Windows).
  2. RELATIVE PATH:./my-package or../my-package.

npm install options:

• --save: It installs package to the package.json file under the dependency section.
• --save-dev: The package is saved under devDependencies.
• --global: It adds the package for all user libraries.

Examples with Output

Example 1: Installing a Local Package

Let's say you have a local package located in the my-local-package directory, and you want to install it in your project.

Output:

 npm notice created a lockfile as package-lock.json. You should commit this file. + my-local-package@1.0.0 added 1 package in 2s 

Example 2: Installing from an Absolute Path

Output:

 + my-local-package@1.0.0 added 1 package in 1s 

Example 3: Installing a Package and Saving to dependencies

Output:

 + my-local-package@1.0.0 added 1 package and updated 1 package in 1s 

In this case, the dependency will be added to the dependencies section of the package.json:

Advantages:

• Local Testing: It means you test your local package before taking it to the npm registry, which can be useful because you can be certain that everything works fine.
• Faster Iterations: In development, it proves to be relatively more convenient to work on a local package and even implementing changes straight into the project.
• Offline Installation: Compared to registry packages, you can install because the package is local, which implies you do not need an internet connection.
• Custom Modifications: You can work on the local package and see the integration of the package on your principal project without having to upload every change.

Use Cases

• Developing Local Packages: Whenever you are generating multiple related packages locally and wish to test out one package in the scope of another.
• Private/Internal Projects: For package that are used within an organization or a company but does not need to be published on the public npm registry.
• Custom Modifications: For changing a package to adapt the feature set to one's project without deployment into an accepted format.

Failure Modes and Effects Analysis

• Missing package.json: Make sure that this local package has an appropriate package.json for configuration of package dependent on a node module. Without this file it will not be recognized by the npm as a package and that is the main reason why we will need it.
• Path Issues: Please, check whether you use the correct relative or absolute path when installing from directory.
• Cache Issues: If it is not the case that the local package is not showing changes, use npm cache clean - force.

Best Practices

• Version Control: It is always necessary to monitor modifications to your local package in version control, such as Git.
• Use Relative Paths: For local dependencies, always use relative paths rather than the absolute paths. It makes sure that other members of the team and the continuous integration tools can solve the dependencies properly.

Conclusion:

In conclusion, by running npm install <directory> command, you can install packages from a specific directory in Node.js. It is useful when developing locally, when testing packages before publishing them or when using company packages. The deed assists to make your work faster especially where you want to fill in a local folder instead of using the npm registry.

The ability in Node.js using npm to install a package from a specified directory is incredibly useful for faster local development and various forms of testing, iteration, etc. It is convenient to store some private packages or to try changes before publishing them in npm.