1. classList (DOMTokenList)

    Method of easily manipulating classes on elements, using the `DOMTokenList` object.

  2. CSS :any-link selector

    The `:any-link` CSS pseudo-class matches all elements that match `:link` or `:visited`

  3. :default CSS pseudo-class

    The `:default` pseudo-class matches checkboxes and radio buttons which are checked by default, `<option>`s with the `selected` attribute, and the default submit button (if any) of a form.

  4. :dir() CSS pseudo-class

    Matches elements based on their directionality. `:dir(ltr)` matches elements which are Left-to-Right. `:dir(rtl)` matches elements which are Right-to-Left.

  5. ::first-letter CSS pseudo-element selector

    CSS pseudo-element that allows styling only the first "letter" of text within an element. Useful for implementing initial caps or drop caps styling.

  6. :focus-visible CSS pseudo-class

    The `:focus-visible` pseudo-class applies while an element matches the `:focus` pseudo-class, and the UA determines via heuristics that the focus should be specially indicated on the element (typically via a “focus ring”).

  7. :focus-within CSS pseudo-class

    The `:focus-within` pseudo-class matches elements that either themselves match `:focus` or that have descendants which match `:focus`.

  8. :has() CSS relational pseudo-class

    Only select elements containing specified content. For example, `a:has(>img)` selects all `<a>` elements that contain an `<img>` child.

  9. :in-range and :out-of-range CSS pseudo-classes

    If a temporal or number `<input>` has `max` and/or `min` attributes, then `:in-range` matches when the value is within the specified range and `:out-of-range` matches when the value is outside the specified range. If there are no range constraints, then neither pseudo-class matches.

  10. :indeterminate CSS pseudo-class

    The `:indeterminate` pseudo-class matches indeterminate checkboxes, indeterminate `<progress>` bars, and radio buttons with no checked button in their radio button group.

  11. :is() CSS pseudo-class

    The `:is()` (formerly `:matches()`, formerly `:any()`) pseudo-class checks whether the element at its position in the outer selector matches any of the selectors in its selector list. It's useful syntactic sugar that allows you to avoid writing out all the combinations manually as separate selectors. The effect is similar to nesting in Sass and most other CSS preprocessors.

  12. selector list argument of :nth-child and :nth-last-child CSS pseudo-classes

    The newest versions of `:nth-child()` and `:nth-last-child()` accept an optional `of S` clause which filters the children to only those which match the selector list `S`. For example, `:nth-child(1 of .foo)` selects the first child among the children that have the `foo` class (ignoring any non-`foo` children which precede that child). Similar to `:nth-of-type`, but for arbitrary selectors instead of only type selectors.

  13. :optional CSS pseudo-class

    The `:optional` pseudo-class matches form inputs (`<input>`, `<textarea>`, `<select>`) which are not `:required`.

  14. :placeholder-shown CSS pseudo-class

    Input elements can sometimes show placeholder text as a hint to the user on what to type in. See, for example, the placeholder attribute in HTML5. The :placeholder-shown pseudo-class matches an input element that is showing such placeholder text.

  15. CSS :read-only and :read-write selectors

    :read-only and :read-write pseudo-classes to match elements which are considered user-alterable

  16. Decorators

    ECMAScript Decorators are an in-progress proposal for extending JavaScript classes. Decorators use a special syntax, prefixed with an `@` symbol and placed immediately before the code being extended.

  17. ECMAScript 2015 (ES6)

    Support for the ECMAScript 2015 specification. Features include Promises, Modules, Classes, Template Literals, Arrow Functions, Let and Const, Default Parameters, Generators, Destructuring Assignment, Rest & Spread, Map/Set & WeakMap/WeakSet and many more.

  18. ES6 classes

    ES6 classes are syntactical sugar to provide a much simpler and clearer syntax to create objects and deal with inheritance.

  19. getElementsByClassName

    Method of accessing DOM elements by class name

  20. Orientation Sensor

    Defines a base orientation sensor interface and concrete sensor subclasses to monitor the device’s physical orientation in relation to a stationary three dimensional Cartesian coordinate system.

  21. relList (DOMTokenList)

    Method of easily manipulating rel attribute values on elements, using the DOMTokenList object (similar to classList).

  22. document api: getelementsbyclassname

  23. domtokenlist api: contains

  24. element api: classname

  25. element api: getelementsbyclassname

  26. svgelement api: classname

  27. usbalternateinterface api: interfaceclass

  28. usbalternateinterface api: interfacesubclass

  29. usbdevice api: deviceclass

  30. usbdevice api: devicesubclass

  31. css selector: class selector (`.classname`)

  32. css selector: first page pseudo-class (`:first`)

  33. css selector: left-hand page pseudo-class (`:left`)

  34. css selector: negation pseudo-class selector (`:not()`)

  35. css selector: right-hand page pseudo-class (`:right`)

  36. html element: object: classid

  37. html attribute: class

  38. javascript classes: constructor

  39. javascript classes: extends

  40. javascript classes: private class fields

  41. javascript classes: private class fields 'in'

  42. javascript classes: private class methods

  43. javascript classes: public class fields

  44. javascript classes: static

  45. javascript classes: static class fields

  46. javascript classes: class static initialization blocks

  47. javascript operator: class

  48. javascript statement: class

  49. attributes: style: class

  50. attributes: style: class: animation support