Publishing a code library

How to publish a Typescript library

npm
,
Typescript
,
package.json

Publishing an npm library is an essential skill for any developer who wants to share their code with the wider community. Whether you're a seasoned developer or just starting with Typescript, creating and publishing an npm package is a valuable experience that will help you learn more about module bundling, package management, and version control.

In this blog post, we'll explore the steps involved in publishing a Typescript npm library and share some best practices for creating high-quality and reusable packages.

Why create a library

You might need a library to enable re-use of functions or React Components across multiple projects or to contribute to the open source community.

Creating a Library

Step 1: Create a Typescript Project

The first step in publishing an npm library is to create a Typescript project that contains the library code. You can create a new project using the npm init command and install the necessary dependencies for your library, such as Typescript and any additional modules that your library depends on.

You will need to add the main and types fields to your package.json file to provide entry points into the library for the compiled JavaScript and type definitions.

An example package.json file:

{
  "name": "my-typescript-library",
  "version": "1.0.0",
  "description": "My Typescript library",
  "main": "dist/index.js",
  "types": "dist/index.d.ts",
  "files": [
    "dist"
  ],
  "repository": {
    "type": "git",
    "url": "git+https://github.com/my-username/my-typescript-library.git"
  },
  "keywords": [
    "typescript",
    "library"
  ],
  "author": "My Name",
  "license": "MIT",
  "bugs": {
    "url": "https://github.com/my-username/my-typescript-library/issues"
  },
  "homepage": "https://github.com/my-username/my-typescript-library#readme",
  "dependencies": {},
  "devDependencies": {},
  "scripts":{
   "build": "tsc"
  }
}

Here are the explanations of the fields:

  • main: This field specifies the entry point for your library, which is the compiled JavaScript file that other developers will import in their projects.
  • types: This field specifies the location of your type definitions, which are the .d.ts files that declare the types for your library.
  • files: This field specifies the list of files and directories that should be included when your library is published to npm.
  • dependencies: This field specifies the list of production dependencies that your library requires to run.
  • devDependencies: This field specifies the list of development dependencies that your library requires to build and test.

You will now need to create your functions and export them from theindex.tsfile at the root of the src folder.

Step 2: Compile Your Typescript Code

After writing your library code in Typescript, you need to compile it into JavaScript that can be used in other projects. You can do this by running the tsc command in your project directory, which will generate the compiled JavaScript files in a separate directory. In the example package.json above you would run the command npm run build

You may want to add a build config called for example tsconfig.build.json, to ignore your test files and provide an output directory, like the one below:

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "outDir": "./dist"
  },
  "exclude": ["node_modules", "**/**.test**"]
}

If you use this technique you will need to add the following to your build script in your package.json file:

"scripts":{
 "build": "tsc --project tsconfig.build.json"
}

Step 3: Bundle Your Library

The next step is to bundle your library code into a single file that can be used by other developers. You can use a bundling tool like Rollup, Webpack, or Parcel to create a single bundle file that contains all the necessary code for your library.

When bundling your library, be sure to configure your bundler to output a UMD (Universal Module Definition) module format, which allows your library to be used in both CommonJS and AMD environments.

Webpack

To use your Typescript library with Webpack, you need to configure the resolve property in your webpack.config.js file to include the .ts and .tsx file extensions, and use the ts-loader plugin to load and transpile your Typescript files:

module.exports = {
  // ...
  resolve: {
    extensions: ['.ts', '.tsx', '.js']
  },
  module: {
    rules: [
      {
        test: /\.tsx?$/,
        use: 'ts-loader',
        exclude: /node_modules/
      }
    ]
  }
  // ...
};

Rollup

To use your Typescript library with Rollup, you need to install the rollup-plugin-typescript2 plugin and configure it in your rollup.config.js file:

import typescript from 'rollup-plugin-typescript2';

export default {
  // ...
  input: 'src/index.ts',
  output: {
    file: 'dist/index.js',
    format: 'umd',
    name: 'MyLibrary'
  },
  plugins: [
    typescript({
      tsconfig: 'tsconfig.json'
    })
  ]
  // ...
};

Parcel

To use your Typescript library with Parcel, you don't need to configure anything special. Simply run the parcel build command in your project directory, and Parcel will automatically detect and build your Typescript files.

parcel build src/index.ts

Parcel is the simplest in terms of configuration as it doesn't require any!

Step 4: Publish Your Library to NPM

Now that you have compiled and bundled your library code, it's time to publish it to npm. To do this, you'll need to create an account on npmjs.com and run the npm login command to authenticate your account.

After logging in, you can run the npm publish command in your project directory to publish your library to npm. Be sure to specify the correct version number for your library using semantic versioning, and include a README file and any necessary documentation in your package.

Step 5: Maintain Your Library

Publishing your library to npm is just the beginning of the process. You'll need to maintain your library and provide updates and bug fixes as necessary.

Be sure to follow best practices for version control and release management, such as using git tags and maintaining a changelog. You should also provide clear documentation and examples for how to use your library, and be responsive to any bug reports or feature requests from users.

Conclusion

Publishing an npm library is a valuable experience for any Typescript developer. By following best practices and using the right tools, you can create high-quality and reusable packages that can be shared with the wider community. By maintaining your library and responding to user feedback, you can also build a reputation as a reliable and responsive developer, and contribute to the growth of the Typescript ecosystem.

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