1. CSS Nesting

    CSS nesting provides the ability to nest one style rule inside another, with the selector of the child rule relative to the selector of the parent rule. Similar behavior previously required a CSS pre-processor.

  2. CSS overscroll-behavior

    CSS property to control the behavior when the scroll position of a scroll container reaches the edge of the scrollport.

  3. CSS Scroll-behavior

    Method of specifying the scrolling behavior for a scrolling box, when scrolling happens due to navigation or CSSOM scrolling APIs.

  4. ES6 Generators

    ES6 Generators are special functions that can be used to control the iteration behavior of a loop. Generators are defined using a `function*` declaration.

  5. High-quality kerning pairs & ligatures

    When used in HTML, the unofficial `text-rendering: optimizeLegibility` CSS property enables high-quality kerning and ligatures in certain browsers. Newer browsers have this behavior enabled by default.

  6. Proxy object

    The Proxy object allows custom behavior to be defined for fundamental operations. Useful for logging, profiling, object visualization, etc.

  7. capturecontroller api: setfocusbehavior

  8. element api: scrollby: `options.behavior` parameter

  9. element api: scrollto: `options.behavior` parameter

  10. element api: scroll: `options.behavior` parameter

  11. fetchevent api: respondwith: change in behavior when specifying the final url of a resource.

  12. htmlmarqueeelement api: behavior

  13. window api: scrollby: `options.behavior` parameter

  14. window api: scrollto: `options.behavior` parameter

  15. window api: scroll: `options.behavior` parameter

  16. css property: content-visibility: transitionable when setting `transition-behavior: allow-discrete`

  17. css property: display: contents: specific behavior of unusual elements when `display: contents` is applied to them

  18. css property: display: transitionable when setting `transition-behavior: allow-discrete`

  19. css property: overscroll-behavior

  20. css property: overscroll-behavior-block

  21. css property: overscroll-behavior-block: auto

  22. css property: overscroll-behavior-block: contain

  23. css property: overscroll-behavior-block: none

  24. css property: overscroll-behavior-inline

  25. css property: overscroll-behavior-inline: auto

  26. css property: overscroll-behavior-inline: contain

  27. css property: overscroll-behavior-inline: none

  28. css property: overscroll-behavior-x

  29. css property: overscroll-behavior-x: auto

  30. css property: overscroll-behavior-x: contain

  31. css property: overscroll-behavior-x: none

  32. css property: overscroll-behavior-y

  33. css property: overscroll-behavior-y: auto

  34. css property: overscroll-behavior-y: contain

  35. css property: overscroll-behavior-y: none

  36. css property: overscroll-behavior: auto

  37. css property: overscroll-behavior: contain

  38. css property: overscroll-behavior: none

  39. css property: scroll-behavior: auto

  40. css property: scroll-behavior: smooth

  41. css property: transition-behavior

  42. css property: transition: `transition-behavior` value

  43. html element: area: `target="_blank"` implies `rel="noopener"` behavior

  44. html element: a: `target="_blank"` implies `rel="noopener"` behavior

  45. html element: marquee: behavior

  46. html attribute: nonce: `nonce` hiding behavior

  47. javascript built-in: intl: datetimeformat: `datetimeformat()` constructor: supports normative optional `chaindatetimeformat` behavior

  48. javascript built-in: intl: numberformat: `numberformat()` constructor: supports normative optional `chainnumberformat` behavior

  49. javascript built-in: object: preventextensions: es2015 behavior for non-object argument

  50. javascript built-in: regexp: sticky: anchored sticky flag behavior per es2015