Also included is an example that will do php-like urlEncode on a string.

function mreplace(str,hash){
var a = [];
for(var key in hash){a[a.length] = key;}
var regexp = a.join(‘|’);
return str.replace( new RegExp(regexp,’g'), function(m,l){ return hash[m] || hash["\\"+m]; });
}

function urlEncode(a){
return mreplace(escape(a),{‘\\/’:'%2F’,'\\?’:'%3F’,'=’:'%3D’,'&’:'%26′,’@':’%40′,’\\s’:'+’});
}

–jim

var html_ents = { '#160':' ', '#161':'¡','#162':'¢','#163':'£','#165':'¥',
	'#167':'§','#169':'©','#171':'«','#174':'®','#177':'±','#180':'´',
	'#181':'µ','#182':'¶','#183':'·','#187':'»','#191':'¿','#192':'À',
	'#193':'Á','#194':'Â','#195':'Ã','#196':'Ä','#197':'Å','#198':'Æ',
	'#199':'Ç','#200':'È','#201':'É','#202':'Ê','#203':'Ë','#204':'Ì',
	'#205':'Í','#206':'Î','#207':'Ï','#209':'Ñ','#210':'Ò','#211':'Ó',
	'#212':'Ô','#213':'Õ','#214':'Ö','#216':'Ø','#217':'Ù','#218':'Ú',
	'#219':'Û','#220':'Ü','#223':'ß','#224':'à','#225':'á','#226':'â',
	'#227':'ã','#228':'ä','#229':'å','#230':'æ','#231':'ç','#232':'è',
	'#233':'é','#234':'ê','#235':'ë','#236':'ì','#237':'í','#238':'î',
	'#239':'ï','#241':'ñ','#242':'ò','#243':'ó','#244':'ô','#245':'õ',
	'#246':'ö','#247':'÷','#248':'ø','#249':'ù','#250':'ú','#251':'û',
	'#252':'ü','#255':'ÿ','#34':'','#38':'&','#60':'<','#62':'>',
	'#8211':'–','#8212':'—','#8364':'€','#96':'`',
	'aacute':'Á','aacute':'á','acirc':'Â','acirc':'â','aelig':'Æ',
	'aelig':'æ','agrave':'À','agrave':'à','amp':'&','aring':'Å',
	'aring':'å','atilde':'Ã','atilde':'ã','auml':'Ä','auml':'ä',
	'ccedil':'Ç','ccedil':'ç','cent':'¢','copy':'©','divide':'÷',
	'eacute':'É','eacute':'é','ecirc':'Ê','ecirc':'ê','egrave':'È',
	'egrave':'è','euml':'Ë','euml':'ë','euro':'€','gt':'>',
	'iacute':'Í','iacute':'í','icirc':'Î','icirc':'î','iexcl':'¡',
	'igrave':'Ì','igrave':'ì','iquest':'¿','iuml':'Ï','iuml':'ï',
	'laquo':'«','lt':'<','mdash':'—','micro':'µ','middot':'·',
	'nbsp':' ','ndash':'–','ntilde':'Ñ','ntilde':'ñ','oacute':'Ó',
	'oacute':'ó','ocirc':'Ô','ocirc':'ô','ograve':'Ò','ograve':'ò',
	'oslash':'Ø','oslash':'ø','otilde':'Õ','otilde':'õ','ouml':'Ö',
	'ouml':'ö','para':'¶','plusmn':'±','pound':'£','quot':'\&quot;',
	'raquo':'»','reg':'®','sect':'§','szlig':'ß','uacute':'Ú',
	'uacute':'ú','ucirc':'Û','ucirc':'û','ugrave':'Ù','ugrave':'ù',
	'uuml':'Ü','uuml':'ü','yen':'¥','yuml':'ÿ'};

function html_entity_decode(str) {

	parts = str.split(/&|;/g);

	for(i=1, stop=parts.length; i<stop; i+=2) {
		parts[i] = html_ents[parts[i]];
	}

	return parts.join('');
}

function init() {

	document.writeln('some &lt;b&gt;bold&lt;/b&gt; text');
	document.writeln('<br><br>

');
	document.writeln('some &lt;b&gt;bold&lt;/b&gt; text'.split(/&|;/));
	document.writeln('<br><br>
');
	document.writeln(html_entity_decode('some &lt;b&gt;bold&lt;/b&gt; text'));
	document.writeln('<br><br>

');
	document.writeln(html_entity_decode('&lt;b&gt;bold&lt;/b&gt; text'));
}

init();

No, I appreciate this is a bit of play.

It tried experimenting with doing a “RegExp.prototype.test()” before the “replace()” to see if that gave any performance improvements, by saving unnecessary “str = str.replace”. No, it was worse!

As operations on immutable things such a strings, I believe, can be very efficient, the str = str.replace, even for a lot of replacements, is very performant, so there does not seem to be any reason to optimise further, for the general case.

Kidding aside, I agree that simple/flexible is better. I was mostly just experimenting and playing here, especially since the standard replacement syntax (shown at the beginning of this post) isn’t that bad to begin with.

var replacements = [
    [/a/g, "b"],
    [/c/g, "d"],
]

String.prototype.multiReplace = function ( replacements ) {
	var str = this, i;
	for (i = 0; i < replacements.length; i++ ) {
		str = str.replace(replacements[i][0], replacements[i][1]);
	}
	return str;
};

This guarantees the order, saves having to generate the RegExp each time, and lets you use different switches.