How to Document JavaScript Projects with JsDuck

Automating API Docs: Best Practices Using JsDuckAutomated API documentation saves developer time, reduces errors, and keeps docs synchronized with the codebase. JsDuck is a documentation tool created by Sencha that generates clean, searchable HTML API documentation from specially formatted comments in JavaScript source files. This article explains how to automate API documentation with JsDuck, covering setup, comment conventions, integration into build pipelines, quality checks, customization, and maintenance practices to keep docs useful and reliable.

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What is JsDuck and when to use it

JsDuck parses JavaScript source files and generates static HTML documentation from JSDuck-style comments. It’s particularly well-suited for:

• Libraries or frameworks written in vanilla JavaScript or Ext JS.
• Projects that want a simple static docs site with search and cross-references.
• Teams preferring documentation generated from source as part of CI/CD.

If you already use JSDoc or another tool with stronger ecosystem integrations, evaluate whether switching to JsDuck is worth it. For Ext JS projects, JsDuck remains a natural fit.

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Installation and basic setup

1. Install Ruby and the gem:
   • JsDuck is distributed as a Ruby gem, so you’ll need Ruby and RubyGems installed.
   • Install with:

     
     gem install jsduck 

2. Create a directory structure:
   • Typical layout:
     • src/ — your JavaScript source
     • docs/ — generated documentation output
     • jsduck.conf — configuration file (optional)
3. Basic generation command:

   
   jsduck src --output docs 

   This scans the src directory and writes HTML files into docs.

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Commenting conventions and best practices

JsDuck reads specially formatted block comments. Use clear, consistent comments to maximize the quality of generated docs.

• Use @class and @constructor for classes: “` /**
  • Represents a user.
  • @class User
  • @constructor
  • @param {Object} config */ function User(config) { … } “`
• Document methods with @method, @param, @return: “` /**
  • Logs in a user.
  • @method login
  • @param {String} username
  • @param {String} password
  • @return {Promise} */ User.prototype.login = function(username, password) { … }; “`
• Use @cfg for configuration options and @event for events.
• Keep descriptions concise and start with a one-line summary followed by more details when necessary.
• Include examples using @example blocks for complex APIs.

Tips:

• Prefer explicit @type and @param types to improve reader understanding.
• Keep comment placement immediate above the function/class declaration.
• Avoid duplicating trivial info; focus on behavior, side effects, and examples.

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Organizing source for clearer docs

Well-structured source makes generated docs easier to navigate:

• Group related classes into directories (e.g., src/models, src/controllers).
• Use index files that export or require related modules so JsDuck can resolve cross-references.
• Name files intentionally: class names should match file names where possible.

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Configuration options and templates

You can control output with command-line flags and a config file. Common options:

• –output: destination folder
• –title: documentation title
• –builtin-classes: include references to built-in JS types
• –external: declare external libraries to avoid documenting them
• –template: specify a custom template to change look & feel

Custom templates allow branding and layout changes. JsDuck templates are HTML with placeholder tags; you can copy the default template and modify it. Keep CSS separate so upgrades are easier.

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Integrating JsDuck into CI/CD

Automation is most valuable when documentation generation runs automatically.

• Add a build step:
  • In npm scripts:

    
    "scripts": { "docs": "jsduck src --output docs" } 

  • Or in your CI config (GitHub Actions, GitLab CI, Jenkins):
    • Install Ruby and gem
    • Run jsduck command
    • Publish artifacts (deploy to GitHub Pages, S3, or internal docs server)
• Generate docs on pushes to main branch or on tags/releases.
• Optionally, generate preview docs for pull requests:
  • Use ephemeral sites (Netlify, Vercel) or store artifacts per PR.
  • This helps reviewers verify that documentation changes accompany code changes.

Example GitHub Actions step (conceptual):

- name: Install Ruby   uses: ruby/setup-ruby@v1 - name: Install JsDuck   run: gem install jsduck - name: Generate docs   run: jsduck src --output docs - name: Deploy docs   run: <deploy to hosting> 

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Quality checks and linting

Treat docs as part of code quality:

• Enforce presence of comments for public APIs:
  • Use a linter or custom script to scan for undocumented exported symbols.
• Validate comment syntax:
  • Create a small test that runs jsduck on a dry run and fails on warnings/errors.
• Check examples compile (if runnable) by executing them in a test harness.
• Review docs in code reviews — require that API changes update docs.

Failing fast in CI prevents drift between code and documentation.

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Versioning and changelogs

• Generate docs per release and keep previous versions accessible.
  • Use versioned subfolders: docs/v1.0.0/, docs/v1.1.0/.
  • Or use a static site generator that supports versioning.
• Include a CHANGELOG.md reflecting API-level breaking changes.
• Tag releases in your repo and trigger doc builds on tags to ensure docs match released code.

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Customization and advanced features

• Cross-references: Use @inheritdoc or @see to link related items.
• Private vs public: Use @private to hide internals. Ensure only intended APIs are visible.
• Search: Default JsDuck includes client-side search; tune it if your API is large (e.g., index only public items).
• Theming: Customize CSS and templates for brand alignment. Keep a lightweight override to ease upgrades.

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Performance and scalability

For large codebases, generation can be slow. Strategies:

• Parallelize generation where possible (split modules and combine outputs).
• Exclude vendor or third-party code with –external.
• Cache intermediate parsing results in CI to avoid full rebuilds every time.

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Common pitfalls and how to avoid them

• Outdated examples: Keep runnable examples in tests or snippets that are executed during CI.
• Missing parameter types: Prefer explicit types; if using TypeScript, consider generating docs from type definitions or keeping JSDuck comments in sync.
• Over-documenting internals: Hide private APIs with @private and document only the public contract.
• Not automating docs deployment: Without automation, docs drift—automate building and publishing.

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Example workflow summary

1. Add JSDuck comments to source as you implement features.
2. Add an npm script and CI step to run jsduck and capture warnings.
3. Generate preview docs for pull requests and full docs on merges/tags.
4. Publish versioned docs to your hosting (GitHub Pages, S3, internal server).
5. Enforce documentation coverage via CI checks and code review.

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Final notes

Automating API docs with JsDuck ensures your documentation stays accurate and discoverable. Focus on consistent comment practices, CI integration, and keeping examples runnable. With a repeatable pipeline, documentation becomes a reliable product artifact rather than an afterthought.