1. EventTarget.addEventListener()

    The modern standard API for adding DOM event handlers. Introduced in the DOM Level 2 Events spec. Also implies support for `removeEventListener`, the [capture phase](https://dom.spec.whatwg.org/#dom-event-capturing_phase) of DOM event dispatch, as well as the `stopPropagation()` and `preventDefault()` event methods.

  2. EOT - Embedded OpenType fonts

    Type of font that can be derived from a regular font, allowing small files and legal use of high-quality fonts. Usage is restricted by the file being tied to the website

  3. hidden attribute

    The `hidden` attribute may be applied to any element, and effectively hides elements similar to `display: none` in CSS.

  4. IndexedDB

    Method of storing data client-side, allows indexed database queries.

  5. IndexedDB 2.0

    Improvements to Indexed DB, including getAll(), renaming stores and indexes, and binary keys.

  6. Path2D

    Allows path objects to be declared on 2D canvas surfaces

  7. Add to home screen (A2HS)

    The ability for a user to "install" a website and use it as if it was a natively installed app. To enable this behaviour, a website must serve a valid Web App Manifest and load it's assets through a [Service Worker](https://caniuse.com/#feat=serviceworkers).

  8. html element: address

  9. html element: dd

  10. html element: dd: nowrap

  11. javascript built-in: atomics: add

  12. javascript built-in: set: add

  13. javascript built-in: temporal api: temporal.zoneddatetime interface

  14. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.add()

  15. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.calendar

  16. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.compare()

  17. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime constructor

  18. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.day

  19. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.dayofweek

  20. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.dayofyear

  21. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.daysinmonth

  22. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.daysinweek

  23. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.daysinyear

  24. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.equals()

  25. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.from()

  26. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.hour

  27. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.hoursinday

  28. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.inleapyear

  29. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.microsecond

  30. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.millisecond

  31. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.minute

  32. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.month

  33. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.monthcode

  34. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.nanosecond

  35. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.offset

  36. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.round()

  37. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.second

  38. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.since()

  39. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.subtract()

  40. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.timezone

  41. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.toinstant()

  42. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.tojson()

  43. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.tostring()

  44. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.until()

  45. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.valueof()

  46. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.weekofyear

  47. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.with()

  48. javascript built-in: temporal api: temporal.zoneddatetime interface: temporal.zoneddatetime.year

  49. javascript built-in: weakset: add

  50. javascript operator: addition (`+`)