Infinite list: Automatically lazy-loads content from a data source as the user scrolls, view-recycling as necessary.
Lazy-load image: Won't load the resource until it is on or near the screen.
Pull to refresh: Recreate the "pull down to refresh" UI from iOS and Android.
Carousel: Side scroller that handles lazy-loading and optionally snaps to elements.
Multi-line ellipsis: Automatically hide text and replace with a fade/ellipsis after a specified number of lines.
Async local storage: Async version of the local storage API.
Navigation drawer: A side bar that can show/hide on smaller devices, similar to iOS and Android components.
Parallax background: An element that creates a parallax scrolling effect between its background and foreground.
Tab UI: A series of tabs that allow the user to switch between different content views.
Sortable list/table: A list or table view that allows sorting by various parameters.
Easier interface for workers: A way of exposing classes and functions from workers to the main thread, wrapped in an async proxy. See https://github.com/GoogleChromeLabs/comlink.
WebSocket stream interface: A modernized interface for WebSockets which interoperates with other streams. https://streams.spec.whatwg.org/#example-both, but productionized.
GZIP: Allows decompressing or compressing data in GZIP format; useful for uploading to servers and for introspecting zipped files.