Understanding npm dependencies version specifiers

When developing a Javascript application, you may find yourself relying on external packages and libraries to achieve your goals. These external packages are known as dependencies, and they are specified in your project’s package.json file.

In the package.json file, dependencies are defined in an object that maps the package name to a version range. The version range is a string that contains one or more space-separated descriptor. These can take on a variety of forms, including version numbers, version ranges, and URLs.

Here are some of the most common version specifiers:

Exact Version

version : This matches the exact version specified.

Example: "lodash": "4.17.20"

Use this when you need to ensure that a specific version of a package is used. This can be useful when you know that a certain version of a package works well with your application and you don’t want any unexpected changes.

Greater Than

>version : This matches any version greater than the specified version.

Example: "react": ">16.0.0"

Use this when you need to ensure that your application is using a version of a package that has certain features or bug fixes. This can be useful when you know that a newer version of a package has improvements that you need.

Greater Than or Equal To

>=version : This matches any version greater than or equal to the specified version.

Example: "axios": ">=0.19.0"

Use this when you need to ensure that your application is using a version of a package that has a certain level of stability. This can be useful when you know that a package has undergone significant changes and you want to ensure that your application is using a stable version.

Less Than

<version : This matches any version less than the specified version.

Example: "moment": "<2.0.0"

Use this when you need to ensure that your application is using a version of a package that does not have certain changes or issues. This can be useful when you know that a newer version of a package has introduced changes that you are not yet ready to use.

Less Than or Equal To

<=version : This matches any version less than or equal to the specified version.

Example: "express": "<=4.17.1"

Use this when you need to ensure that your application is using a version of a package that is compatible with other packages in your application. This can be useful when you know that a newer version of a package may introduce compatibility issues with other packages.

Approximately Equivalent

~version : This matches any version that is approximately equivalent to the specified version, according to semantic versioning rules. This means that it accepts new patch versions but not minor or major versions.

Example: "react-dom": "~16.13.1"

Use this when you need to ensure that your application is using a version of a package that is compatible with other packages in your application, but you are not sure of the exact version you need. This can be useful when you want to ensure that your application uses a version of a package that is compatible with other packages, but you don’t want to specify an exact version.

Compatible With

^version : This matches any version that is compatible with the specified version, according to semantic versioning rules. This means that it accepts new patch and minor versions but not major versions.

Example: "react-redux": "^7.2.0"

Version Range

version1 - version2 : This matches any version within the specified range, including version1 and version2.

Example: "webpack": "4.0.0 - 4.43.0"

Use this when you need to ensure that your application is using a version of a package that falls within a certain range. This can be useful when you know that a certain range of versions work well with your application.

Logical OR

range1 || range2 : This matches any version that satisfies either range1 or range2.

Example: "babel-core": "6.x || 7.x"

Use this when you need to ensure that your application is using a version of a package that satisfies one of several conditions. This can be useful when you know that multiple versions of a package will work with your application and you want to allow any of them.

Any Version

* : This matches any version.

Example: "jest": "*"

Use this when you want to allow any version of a package to be used. This can be useful when you don’t have specific requirements for a package and you are comfortable with any version.

Empty String

"" : This is the same as *, matching any version.

Example: "chalk": ""

Use this when you want to allow any version of a package to be used. This is the same as using the *

Git URL

git... : This specifies a Git URL as a dependency.

Example: "my-package": "git://github.com/user/my-package.git"

Use this when you need to use a specific version of a package that is not available on the public NPM registry. This can be useful when you need to use a fork of a package or a version that has not yet been published.

GitHub URL

user/repo : This specifies a GitHub URL as a dependency.

Example: "my-package": "user/repo"

Use this when you need to use a specific version of a package that is hosted on GitHub. This can be useful when you want to use a version of a package that is not available on the public NPM registry.

Tag

tag : This specifies a specific version that has been tagged and published.

Example: "my-package": "latest"

Use this when you need to ensure that your application is using a specific version of a package that has been tagged and published. This can be useful when you want to ensure that your application is using a stable version of a package.

Local Path

path/path/path : This specifies a local path as a dependency.

Example: "my-package": "file:../my-package"

Use this when you need to use a package that is not available on the public NPM registry. This can be useful when you need to use a package that is not yet published or when you are developing a package locally.

Conclusion

It’s important to note that you should not include test harnesses, transpilers, or other development time tools in your dependencies object. Instead, use the devDependencies object to specify these dependencies.

By understanding how to specify version ranges in your package.json file, you can ensure that your Node.js application is using the correct versions of its dependencies.