Specifying dependencies and devDependencies in a package.json file
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To specify the packages your project depends on, you must list them as "dependencies" or "devDependencies" in your package's package.json file. When you (or another user) run npm install, npm will download dependencies and devDependencies that are listed in package.json that meet the semantic version requirements listed for each. To see which versions of a package will be installed, use the semver calculator.
"dependencies": Packages required by your application in production."devDependencies": Packages that are only needed for local development and testing.
Adding dependencies to a package.json file
You can add dependencies to a package.json file from the command line or by manually editing the package.json file.
Adding dependencies to a package.json file from the command line
To add dependencies and devDependencies to a package.json file from the command line, you can install them in the root directory of your package using the --save-prod flag (also -S) for dependencies (the default behavior of npm install) or the --save-dev flag (also -D) for devDependencies.
To add an entry to the "dependencies" attribute of a package.json file, on the command line, run the following command:
npm install <package-name> [--save-prod]
To add an entry to the "devDependencies" attribute of a package.json file, on the command line, run the following command:
npm install <package-name> --save-dev
Manually editing the package.json file
To add dependencies to a package.json file, in a text editor, add an attribute called "dependencies" that references the name and semantic version of each dependency:
{"name": "my_package","version": "1.0.0","dependencies": {"my_dep": "^1.0.0","another_dep": "~2.2.0"}}
To add devDependencies to a package.json file, in a text editor, add an attribute called "devDependencies" that references the name and semantic version of each devDependency:
"name": "my_package","version": "1.0.0","dependencies": {"my_dep": "^1.0.0","another_dep": "~2.2.0"},"devDependencies" : {"my_test_framework": "^3.1.0","another_dev_dep": "1.0.0 - 1.2.0"}
