const

Declares a constant with block level scope

Scoped Styles: the @scope rule

Allows CSS rules to be scoped to part of the document, with upper and lower limits described by selectors.

CSS Containment

The CSS `contain` property lets developers limit the scope of the browser's styles, layout and paint work for faster and more efficient rendering.

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.

Gyroscope

Defines a concrete sensor interface to monitor the rate of rotation around the device’s local three primary axes.

let

Declares a variable with block level scope

Scoped attribute

Deprecated method of allowing scoped CSS styles using a "scoped" attribute. Now [removed from the specification](https://github.com/whatwg/html/issues/552) and replaced by the [@scope CSS rule](/css-cascade-scope).

html element: th: scope