classList (DOMTokenList)

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

: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.

: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.

::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.

: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”).

:focus-within CSS pseudo-class

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

:has() CSS relational pseudo-class

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

: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.

: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.

: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.

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.

:optional CSS pseudo-class

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

: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.

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.

ES6 classes

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

getElementsByClassName

Method of accessing DOM elements by class name

domtokenlist api: contains

element api: classname

svgelement api: classname

css property: view-transition-class

css property: view-transition-class: none

css selector: class selector (`.classname`)

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

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

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

css selector: custom state pseudo-class selector (`:state()`)

html element: object: classid

html attribute: class

javascript classes: constructor

javascript classes: extends

javascript classes: private class fields

javascript classes: private class fields 'in'

javascript classes: private class methods

javascript classes: public class fields

javascript classes: `static` keyword

javascript classes: `static` keyword: static class fields

javascript classes: `static` keyword: static initialization blocks

javascript operator: class

regular_expressions: character class: `[...]`, `[^...]`

regular_expressions: character class escape: `\d`, `\d`, `\w`, `\w`, `\s`, `\s`

regular_expressions: unicode character class escape: `\p{...}`, `\p{...}`

javascript statement: class

global_attributes: class

global_attributes: class: animation support