TLDR: Semantic Release

The more an NPM library becomes "stable", the more publishing a new version of it on NPM becomes quite a boring task:

Someone sends a PR for a small bugfix/improvement
The PR gets reviewed and merged
The library version number gets bumped and released
Someone writes the changelog

Enter semantic-release, a powerful set of tools for fully automating version management and package publishing.

With semantic-release you can easily automate the flow described above by letting it handle for you the release process in your Continuous Integration.

First, install semantic-release:

npm install --save-dev semantic-release

npm install --save-dev semantic-release

The semantic-release package has almost everything you need... but to get the most of it you'll also need an additional plugin (that for some reason is not included by default):

npm install --save-dev @semantic-release/git

npm install --save-dev @semantic-release/git

Next step, create the semantic-release configuration file, which is a JSON file name .releaserc file at the root of you project:

{
  "plugins": [
    "@semantic-release/commit-analyzer",
    "@semantic-release/release-notes-generator",
    "@semantic-release/npm",
    "@semantic-release/github",
    "@semantic-release/git"
  ]
}

{
  "plugins": [
    "@semantic-release/commit-analyzer",
    "@semantic-release/release-notes-generator",
    "@semantic-release/npm",
    "@semantic-release/github",
    "@semantic-release/git"
  ]
}

Let's now move to the CI setup. In my case I'm using CircleCI, but semantic-release is unopinionated on this subject.

Create (or update) a .circle/config.yml file for running semantic-release after your tests:

# Example config
version: 2
 
jobs:
  test:
    docker:
      - image: circleci/node:10
    steps:
      - checkout
      - run: npm install
      - run: npm test
 
  release:
    docker:
      - image: circleci/node:10
    steps:
      - checkout
      - run: npm install
      - run: npx semantic-release
 
workflows:
  version: 2
  test_and_release:
    # Run the test jobs first, then the release only when all the test jobs are successful
    jobs:
      - test
      - release:
          requires:
            - test

# Example config
version: 2
 
jobs:
  test:
    docker:
      - image: circleci/node:10
    steps:
      - checkout
      - run: npm install
      - run: npm test
 
  release:
    docker:
      - image: circleci/node:10
    steps:
      - checkout
      - run: npm install
      - run: npx semantic-release
 
workflows:
  version: 2
  test_and_release:
    # Run the test jobs first, then the release only when all the test jobs are successful
    jobs:
      - test
      - release:
          requires:
            - test

semantic-release requires two environment variables to run:

GH_TOKEN: An NPM token NPM token create.
NPM_TOKEN: GitHub personal authentication token.

Now, whenever a new PR gets merged in your master branch your CI runs the tests and, if they succesfull, it runs the semantic-release process, which:

Checks the commit message (@semantic-release/commit-analyzer): semantic-release determines how to bump the library version (major/minor/patch, following the semver) based on the commit messages used in the merged PR. This means that when merging a PR you should make sure it follows the Angular Comment Message Convention, which is the default convention used by semantic-release.
Creates a changelog (@semantic-release/release-notes-generator): based on the commit messages above, semantic-release generates a changelog.
Bumps and publish the new version on NPM (@semantic-release/npm): semantic-release bumps the version number of the library and publishes it on NPM (thanks to the NPM_TOKEN env var)
Publish the release on GitHub (@semantic-release/github): semantic-release publishes on GitHub a new release with the changelog that was previously generated
Commit the bumped package version (@semantic-release/git): semantic-release commits on the repo the changes generated in the CI (the most important one is the package.json version bump)

That's it!

I tried to keep this post as short as possible, you can find more information in the semantic-release GitBook.