Javascript Package - Package.json

1 - About

Package.json is used by npm to store metadata for projects published as npm modules.

Package.json:

  • serves as documentation for what packages your project depends on.
  • allows you to specify the versions of a package that your project can use using semantic versioning rules.
  • makes the build reproducible

See Reference

3 - Syntax

Mandatory:

  • “name”: all lowercase one word, no spaces dashes and underscores allowed
  • “version” in the form of x.x.x follows semver spec

Optional:

  • main.js: the entry point when the package is used.
  • description. The description helps people find your package on npm search. If there is no description field in the package.json, npm uses the first line of the README.md or README instead.

Example:


{
  "name": "my_package",
  "description": "",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "repository": {
    "type": "git",
    "url": "https://github.com/ashleygwilliams/my_package.git"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "bugs": {
    "url": "https://github.com/ashleygwilliams/my_package/issues"
  },
  "homepage": "https://github.com/ashleygwilliams/my_package"
  "dependencies": {
    "my_dep": "^1.0.0"
  },
  "devDependencies" : {
    "my_test_framework": "^3.1.0"
  }
}

3.1 - Scripts

3.2 - Dependency

3.3 - Import

  • main: main script
  • module: define where to find the module file named by the name properties (use when importing to locate the module)

"module": "src/index.js",  

  • browser defines the location of module that are only available inside the browsers.

"browser": {
    "module-a": false,
    "./server/only.js": "./shims/server-only.js"
}

The import order of precedence is defined in resolve-mainfields for webpack


module.exports = {
  //...
  resolve: {
    mainFields: ['browser', 'module', 'main']
  }
};

4 - Management

4.1 - Create


yarn init
# optionaly
npm init

4.2 - Modify Config


npm set init.author.email "[email protected]"
npm set init.author.name "ag_dubs"
npm set init.license "MIT"


Your Name <[email protected]> (http://example.com)

4.3 - Add dependency

To add dependency, use the save and save dev flag of npm install. See Javascript Package.

  • For dependencies

npm install <package_name> --save

  • For dev-dependencies (development and testing)

npm install <package_name> --save-dev

4.4 - Script

The script section of the package.json allows to start command. See NPM - Script

4.5 - Pass the version to your library

How to pass the version to your library


myLib.VERSION = require('../package.json').version;

5 - Documentation / Reference


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