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.
The `find()` method returns the value of the first item in the array based on the result of the provided testing function.
The `findIndex()` method returns the index of the first element in the array that satisfies the provided testing function.
Determines whether or not an array includes the given value, returning a boolean value (unlike `indexOf`).
DOM node method to remove the node itself from the document.
Compares the relative position of two nodes to each other in the DOM tree.
console.time and console.timeEnd
Functions for measuring performance
CSS Filter Effects
Method of applying filter effects using the `filter` property to elements, matching filters available in SVG. Filter functions include blur, brightness, contrast, drop-shadow, grayscale, hue-rotate, invert, opacity, sepia and saturate.
CSS 2.1 selectors
Basic CSS selectors including: `*` (universal selector), `>` (child selector), `:first-child`, `:link`, `:visited`, `:active`, `:hover`, `:focus`, `:lang()`, `+` (adjacent sibling selector), `[attr]`, `[attr="val"]`, `[attr~="val"]`, `[attr|="bar"]`, `.foo` (class selector), `#foo` (id selector)
The CSS.supports() static method returns a Boolean value indicating if the browser supports a given CSS feature, or not.
Date method to generate a language sensitive representation of a given date, formatted based on a specified locale and options.
Read-only property that returns the ratio of the (vertical) size of one physical pixel on the current display device to the size of one CSS pixel.
Method to programmatically trigger a DOM event.
`document.currentScript` returns the `<script>` element whose script is currently being processed.
document.evaluate & XPath
Allow nodes in an XML/HTML document to be traversed using XPath expressions.
DOM method that returns the current element if it matches the given selector, or else the closest ancestor element that matches the given selector, or else null.
Given coordinates for a point relative to the viewport, returns the element that a click event would be dispatched at if the user were to click the point (in other words, the element that hit-testing would find).
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.
The includes() method determines whether one string may be found within another string, returning true or false as appropriate.
Method to get the size and position of an element's bounding box, relative to the viewport.
Method of generating cryptographically random values.
Returns the number of logical cores of the user's CPU. The value may be reduced to prevent device fingerprinting or because it exceeds the allowed number of simultaneous web workers.
HEVC/H.265 video format
The High Efficiency Video Coding (HEVC) compression standard is a video compression format intended to succeed H.264
Improvements to Indexed DB, including getAll(), renaming stores and indexes, and binary keys.
A property representing the text within a DOM element and its descendants. As a getter, it approximates the text the user would get if they highlighted the contents of the element with the cursor and then copied to the clipboard.
Element.insertAdjacentElement() & Element.insertAdjacentText()
Methods for inserting an element or text before or after a given element, or appending or prepending an element or text to a given element's list of children.
Inserts a string of HTML into a specified position in the DOM relative to the given element.
Iteration on the original API that also reports if the element is covered by another element or has filters applied to it. Useful for blocking clickjacking attempts or tracking ad exposure.
API for plural sensitive formatting and plural language rules.
JPEG XL image format
A modern image format optimized for web environments. JPEG XL generally has better compression than [WebP](/webp), JPEG, PNG and GIF and is designed to supersede them. JPEG XL competes with [AVIF](/avif) which has similar compression quality but fewer features overall.
A `KeyboardEvent` property representing the physical key that was pressed, ignoring the keyboard layout and ignoring whether any modifier keys were active.
A `KeyboardEvent` property whose value is a string identifying the key that was pressed. Covers character keys, non-character keys (e.g. arrow keys), and dead keys.
A legacy `KeyboardEvent` property that is equivalent to either `KeyboardEvent.keyCode` or `KeyboardEvent.charCode` depending on whether the key is alphanumeric.
MPEG-4/H.264 video format
Commonly used video compression format.
The `Object.entries()` method creates a multi-dimensional array of key value pairs from the given object.
The `Object.values()` method returns an array of a given object's own enumerable property values.
Ogg Vorbis audio format
Vorbis is a free and open source audio format, most commonly used with the Ogg container.
The `padStart()` and `padEnd()` methods pad the current string with a given string (eventually repeated) so that the resulting string reaches a given length. The pad is applied from the start (left) of the current string for `padStart()`, and applied from the end (right) of the current string for `padEnd()`.
When the promise is settled, whether fulfilled or rejected, the specified callback function is executed.
If the element is fully within the visible area of the viewport, it does nothing. Otherwise, the element is scrolled into view. A proprietary variant of the standard `Element.scrollIntoView()` method.
SVG (basic support)
Method of displaying basic Vector Graphics features using the embed or object elements. Refers to the SVG 1.1 spec.
DOM Node property representing the text content of a node and its descendants
Version 1.1 of the Transport Layer Security (TLS) protocol.
Version 1.2 of the Transport Layer Security (TLS) protocol. Allows for data/message confidentiality, and message authentication codes for message integrity and as a by-product message authentication.
Version 1.3 (the latest one) of the Transport Layer Security (TLS) protocol. Removes weaker elliptic curves and hash functions.
Next version of WebGL. Based on OpenGL ES 3.0.
WebP image format
Image format (based on the VP8 video format) that supports lossy and lossless compression, as well as animation and alpha transparency. WebP generally has better compression than JPEG, PNG and GIF and is designed to supersede them. [AVIF](/avif) and [JPEG XL](/jpegxl) are designed to supersede WebP.
WOFF - Web Open Font Format
Compressed TrueType/OpenType font that contains information about the font's source.
WOFF 2.0 - Web Open Font Format
TrueType/OpenType font that provides better compression than WOFF 1.0.
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