String.prototype.encodeHTMLEntities, Encoding HTML Entities with JavaScript

String.prototype.encodeHTMLEntities.js

// String.prototype.encodeHTMLEntities
(function () {
	'use strict';

	var
	data = '34quot38amp39apos60lt62gt160nbsp161iexcl162cent163pound164curren165yen166brvbar167sect168uml169copy170ordf171laquo172not173shy174reg175macr176deg177plusmn178sup2179sup3180acute181micro182para183middot184cedil185sup1186ordm187raquo188frac14189frac12190frac34191iquest192Agrave193Aacute194Acirc195Atilde196Auml197Aring198AElig199Ccedil200Egrave201Eacute202Ecirc203Euml204Igrave205Iacute206Icirc207Iuml208ETH209Ntilde210Ograve211Oacute212Ocirc213Otilde214Ouml215times216Oslash217Ugrave218Uacute219Ucirc220Uuml221Yacute222THORN223szlig224agrave225aacute226acirc227atilde228auml229aring230aelig231ccedil232egrave233eacute234ecirc235euml236igrave237iacute238icirc239iuml240eth241ntilde242ograve243oacute244ocirc245otilde246ouml247divide248oslash249ugrave250uacute251ucirc252uuml253yacute254thorn255yuml402fnof913Alpha914Beta915Gamma916Delta917Epsilon918Zeta919Eta920Theta921Iota922Kappa923Lambda924Mu925Nu926Xi927Omicron928Pi929Rho931Sigma932Tau933Upsilon934Phi935Chi936Psi937Omega945alpha946beta947gamma948delta949epsilon950zeta951eta952theta953iota954kappa955lambda956mu957nu958xi959omicron960pi961rho962sigmaf963sigma964tau965upsilon966phi967chi968psi969omega977thetasym978upsih982piv8226bull8230hellip8242prime8243Prime8254oline8260frasl8472weierp8465image8476real8482trade8501alefsym8592larr8593uarr8594rarr8595darr8596harr8629crarr8656lArr8657uArr8658rArr8659dArr8660hArr8704forall8706part8707exist8709empty8711nabla8712isin8713notin8715ni8719prod8721sum8722minus8727lowast8730radic8733prop8734infin8736ang8743and8744or8745cap8746cup8747int8756there48764sim8773cong8776asymp8800ne8801equiv8804le8805ge8834sub8835sup8836nsub8838sube8839supe8853oplus8855otimes8869perp8901sdot8968lceil8969rceil8970lfloor8971rfloor9001lang9002rang9674loz9824spades9827clubs9829hearts9830diams338OElig339oelig352Scaron353scaron376Yuml710circ732tilde8194ensp8195emsp8201thinsp8204zwnj8205zwj8206lrm8207rlm8211ndash8212mdash8216lsquo8217rsquo8218sbquo8220ldquo8221rdquo8222bdquo8224dagger8225Dagger8240permil8249lsaquo8250rsaquo8364euro',
	charCodes = data.split(/[A-z]+/),
	entities = data.split(/\d+/).slice(1);

	String.prototype.encodeHTMLEntities = function encodeHTMLEntities(all) {
		return all ? this.replace(/[\u00A0-\u2666<>"'&]/g, function (match) {
			var charCode = String(match.charCodeAt(0)), index = charCodes.indexOf(charCode);

			return '&' + (entities[index] ? entities[index] : '#' + charCode) + ';';
		}) : this.replace(/[\u00A0-\u2666]/g, function (match) {
			var charCode = String(match.charCodeAt(0)), index = charCodes.indexOf(charCode);

			return '&' + (entities[index] ? entities[index] : '#' + charCode) + ';';
		}).replace(/(^|>)[^<>]+(<|$)/g, function (match) {
			return match.replace(/"|'/g, function (match) {
				return '&' + entities[charCodes.indexOf(String(match.charCodeAt(0)))] + ';';
			});
		});
	};
})();

Got a decode version?

A 'decoded' version is there: http://stackoverflow.com/questions/1354064/how-to-convert-characters-to-html-entities-using-plain-javascript from user Chris. 34quo38amp is 34->quot, 38->amp and so on...

Why stop at U+2666? Seems arbitrary. Anyway, for a solution that correctly encodes all except safe & printable ASCII symbols in the input (including astral symbols!), and implements all named character references (not just those in HTML4), use the he library (relevant Stack Overflow answer).

License?