Associated Technologies - HTML5 Mastery: Semantics, Standards, and Styling - page 359

Web workers
Web workers are making computationally intensive tasks on the Web a little less painful.
JavaScript is a single-threaded language, meaning a script that takes a lot of process-
ing power could completely paralyze any user-interactive scripts that may be running.
Using a web worker, a new thread can be spawned that runs a script without interrupting
the processing of UI interactions or other events in the main script. Web workers come
in two flavors: dedicated workers and shared workers. Shared workers are more power-
ful than dedicated workers because they can communicate with multiple scripts, while a
dedicated worker responds only to the script that spawned it in the first place.
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3 See http://sqlite.org .
4 See www.w3.org/TR/IndexedDB/ .
Web Sockets API
The Web Sockets API 5 is a specification that defines a protocol for providing two-way
communication with a remote host. The Web's roots have traditionally been essentially
one-way. A server sends a page to a client web browser, and then nothing happens
between the two until the user clicks a link and requests another page. What a web sock-
et provides is an open connection over which data can be sent from the client to the serv-
er at any time after the page has loaded, and vice versa. This could be used, for example,
to create multiplayer online games or applications, because data can be sent to the server
from one client and distributed to all other clients connected to the same server.
Video conferencing and peer-to-peer communication
A project is underway to create a specification for video conferencing between two web
browsers. This is a major area of difference between the W3C HTML5 and WHATWG
HTML specifications, because it is included in the WHATWG version but omitted from
the W3C specification. Instead, the W3C has a separate specification named “WebRTC
1.0: Web Real-time Communication Between Browsers.” 6 Since both specifications are
in draft status, it is not inconceivable that the version included in the WHATWG HTML
draft may well be spun off into a separate specification in the future, as has happened at
the W3C.
Anyway, administration issues aside, the actual technology for enabling video con-
ferencing requires that two separate web browsers gather video and audio and stream it