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Breaking change: Puppeteer no longer uses Node’s EventEmitter library

As part of our work to make Puppeteer agnostic of its environment we are removing the dependency on Node’s EventEmitter in favour of an event emitter that is not tied to Node. Under the hood we use Mitt, but we extend Mitt with additional functionality to match most of the methods that Node’s EventEmitter provides. The following methods have been removed from Puppeteer classes that extend EventEmitter:

  • eventNames()
  • getMaxListeners()
  • listeners(eventName)
  • prependListener
  • prependOnceListener
  • setMaxListeners(n)
  • rawListeners(eventName)

Additionally all the static methods on the EventEmitter class are not supported:

  • listenerCount(emitter, eventName)
  • defaultMaxListeners
  • errorMonitor

Node’s EventEmitter emitted a newListener event when a listener was added and a removeListener event when one was removed. These are not supported and will not be emitted.

New features and improvements

  • Send/receive debug logs are now split out into separate channels making the logs much clearer (#6017)
  • You can now call isJavaScriptEnabled() on a Puppeteer page to find out if JS is enabled on the page (#5993)

Bug fixes

  • Puppeteer is now much better at killing lingering browser processes, especially when you exit a test run with Ctrl-C (#6011)

Behind the scenes

  • We've started work on a new documentation system that uses TSDoc to generate documentation from our source code and have been porting documentation into code accordingly.

Raw notes

5493494 - chore: mark version 4.0.0
03ab1c1 - fix: improve Ctrl + C support (#6011)
b659969 - chore: migrate away from Node's EventEmitter (#5979)
6e060ce - fix(connection): separate send/receive debug logging (#6017)
c701ea1 - chore: fix npm test command (#6010)
398c16d - chore: fix docs linter (#6009)
4205ff7 - docs(api): remove subheader for non-namespace
3d56a9e - chore: add test configuration options for running tests against multiple products (#5964)
5c91dfb - chore: move index.js into src (#6007)
8a099a0 - docs: replace @return with @returns (#6006)
23f18d8 - docs(new): start documenting the Page class (#6001)
c1d7be3 - docs(api): add copy-pasting text example to Mouse class (#6000)
91eb745 - chore: ensure new-docs are up to date (#5994)
b86ff21 - feat(api): add Page.isJavaScriptEnabled + mark properties as private (#5993)
354f942 - feat: improve error reporting on aarch64 (#5167)
9c656d4 - chore: remove prefers-color-scheme: no-preference (#5990)
83c29d9 - chore: clean lib when running tsc (#5982)
ca8b0d6 - feat(new-docs): migrate Dialog documentation to TSDoc (#5981)
0b3d52a - feat(new-docs): add TSDoc comments to Accessibility (#5971)
086c089 - chore: commit base new-docs (#5973)
0032420 - chore: Introduce API Extractor and start generating documentation (#5967)
ef63c64 - test: check installation with Firefox (#5965)
c2d32b1 - chore: rename image assets
a84e07c - chore: increase readability of Puppeteer diagram (#5947)
58d1eab - chore: mark version v3.3.0-post (#5960)