HTML sanitizer

Demo of HTML sanitizer in JS, using whitelist based approach. Nothing is allowed through that isn't recognized as safe; anything else is simply HTML encoded, optionally with hints as to how to fix it (for use in authoring interfaces.) Proof of concept; validators need some cleanup and the code style is moderately atrocious. I guess I hadn't yet developed an allergy to global variables in 2008.

Sample text and image are from Wikipedia, licensed from various authors under the Creative Commons Attribution Share-Alike 3.0 license.

The alewife (Alosa pseudoharengus) is an <a href="https://en.wikipedia.org/wiki/Anadromous">anadromous</a> species of <a href="https://en.wikipedia.org/wiki/Herring">herring</a> found in North America. It is one of the "typical" North American shads, attributed to the subgenus Pomolobus of the genus Alosa. It is best known for its invasion of the Great Lakes by using the Welland Canal to bypass Niagara Falls. Here, its population surged, peaking between the 1950s and 1980s to the detriment of many native species of fish. In an effort to control them biologically, <a href="https://en.wikipedia.org/wiki/Oncorhynchus" title="Oncorhynchus">Pacific salmon</a> were introduced, only partially successfully. As a marine fish, the alewife is a US National Marine Fisheries Service "Species of Concern".

<h2>Description</h2>
Alewives reach a maximum length of about 40 cm (16 in), but have an average length of about 25 cm (10 in). The front of the body is deep and larger than other fish found in the same waters, and its common name is said to come from comparison with a corpulent female tavernkeeper ("ale-wife").[3]

<h2>Distribution</h2>
In southwestern Nova Scotia, it is called a kiack (or kyack). In Atlantic Canada it is known as the gaspereau, from the Acadian French word gasparot, first mentioned by Nicolas Denys. William Francis Ganong, New Brunswick biologist and historian, wrote:

<blockquote>
Gaspereau, or Gasparot. Name of a common salt-water fish of Acadia
(also called alewife), first used, so far as I can find, by Denys in
1672. Nowhere can I find any clue to its origin. It seems not to be
Indian.
</blockquote>

In eastern Massachusetts, Alewife Brook flows through Arlington, Cambridge, and Somerville to the Mystic River. The brook gives its name to the Alewife Brook Parkway and the Alewife Brook Reservation. The Red Line (MBTA) of Boston's T ends at Alewife station, so the name of this fish adorns the front of every northbound Red Line train.

(Nothing here yet.)