Programatic Accent Reduction in JavaScript (aka text normalization or unaccenting)

Question

I need to compare 2 strings as equal such as these:

Lubeck == Lübeck

In JavaScript.

Why? Well, I have an auto-completion field that's going out to a Java service using Lucene, where place names are stored naturally (as Lübeck), but also indexed as normalized text,

import sun.text.Normalizer;
oDoc.setNameLC = Normalizer.normalize(oLocName, Normalizer.DECOMP, 0)
    .toLowerCase().replaceAll("[^\\p{ASCII}]","");

This way some-one who doesn't know to type "Mèxico" can type "mexico" and get a match which returns "Mèxico" (among a lot of other possible hits, like "Café Mèxico, Dubai, UAE").

Now the thing is I don't have the ability to change the service to do any highlighting on the server side, therefore I am highlighting on the client JavaScript side with something like:

return result.replace( input.replace(/[aeiou]/g,"."), "<b>$1</b>");

It's a little more fancy because I am escaping special regex characters in the input. This is fine for simple one word matches at the beginning of a hit, but it really breaks down if you suddenly wish to support multi-word matches like "london cafe":

input = input.strip().toLowerCase(); //fyi prototype's strip is like trim
re = new RegEx(input.replace(/[aeiou]/g,".").replace(/\s+/g,"|"),"gi");
return result.replace(re, "<b>$1</b>");

This doesn't work for say "london ca" (was typing london cafe), because it would mark "Jack London Cabin, Dawson City, Canada" as: "Ja<b>ck</b> <b>London</b> <b>ca</b>bin, Dawson <b>Ci</b>ty, <b>Ca<b/>nada" [note the "ck" and "Ci" particularly]

Therefore I'm sort of looking for something that's not as crazy as:

input = input.strip().toLowerCase();
input = input.replace(/a/g,"[ÀàÁáÂâÃãÄäÅåÆæĀāĂ㥹]");
input = input.replace(/e/g,"[ÈèÉéÊêËëĒēĔĕĖėĘęĚě]");
// ditto for i, o, u, y, c, n, maybe also d, g, h, j, k, l, r, s, t, w, z 
re = new RegEx(input.replace(/\s+/g,"|"),"gi");
return result.replace(re, "<b>$1</b>");

Is there a compiled table I can refer to mapping a range of characters which are accented versions of an other character to that character, by which I don't mean the plain unicode chart. And if so, could I avoid using weird, possibly slow, RegEx statements?

About the bounty:
Before I started a bounty there were two answers, the one pointing me to doing it in Ruby, and the one that MizzardX wrote which was a completion of the basic form I'd put in my question. Now don't get me wrong, I really appreciate working it out as completely as he did, but I just wished that there might be another way. It seems so far that everyone who's dropped by to look at the question and answer has decided that MizzardX covers it just fine, or that they have no different approach. I would be interested in a different approach, and if it simply isn't available before the bounty closes, MizzardX will win the bounty (though in a cruel twist, his edits mad it a community wiki answer, so I'm not sure if he'll get the bounty!)

Savick

Good question. Something like this would be useful in javascript autocompletion scripts, like jQuery UI's autocomplete plugin: docs.jquery.com/UI/Autocomplete – Byelaw

similar question for ruby: #225971 – Kostival

still on this problem 11 months later? bummer. – Archaeology

re: 11 months. It sort of came up again. – Savick

Answer 1

/**
 * Creates a RegExp that matches the words in the search string.
 * Case and accent insensitive.
 */
function make_pattern(search_string) {
    // escape meta characters
    search_string = search_string.replace(/([|()[{.+*?^$\\])/g,"\\$1");

    // split into words
    var words = search_string.split(/\s+/);

    // sort by length
    var length_comp = function (a,b) {
        return b.length - a.length;
    };
    words.sort(length_comp);

    // replace characters by their compositors
    var accent_replacer = function(chr) {
        return accented[chr.toUpperCase()] || chr;
    }
    for (var i = 0; i < words.length; i++) {
        words[i] = words[i].replace(/\S/g,accent_replacer);
    }

    // join as alternatives
    var regexp = words.join("|");
    return new RegExp(regexp,'g');
}

var accented = {
    'A': '[Aa\xaa\xc0-\xc5\xe0-\xe5\u0100-\u0105\u01cd\u01ce\u0200-\u0203\u0226\u0227\u1d2c\u1d43\u1e00\u1e01\u1e9a\u1ea0-\u1ea3\u2090\u2100\u2101\u213b\u249c\u24b6\u24d0\u3371-\u3374\u3380-\u3384\u3388\u3389\u33a9-\u33af\u33c2\u33ca\u33df\u33ff\uff21\uff41]',
    'B': '[Bb\u1d2e\u1d47\u1e02-\u1e07\u212c\u249d\u24b7\u24d1\u3374\u3385-\u3387\u33c3\u33c8\u33d4\u33dd\uff22\uff42]',
    'C': '[Cc\xc7\xe7\u0106-\u010d\u1d9c\u2100\u2102\u2103\u2105\u2106\u212d\u216d\u217d\u249e\u24b8\u24d2\u3376\u3388\u3389\u339d\u33a0\u33a4\u33c4-\u33c7\uff23\uff43]',
    'D': '[Dd\u010e\u010f\u01c4-\u01c6\u01f1-\u01f3\u1d30\u1d48\u1e0a-\u1e13\u2145\u2146\u216e\u217e\u249f\u24b9\u24d3\u32cf\u3372\u3377-\u3379\u3397\u33ad-\u33af\u33c5\u33c8\uff24\uff44]',
    'E': '[Ee\xc8-\xcb\xe8-\xeb\u0112-\u011b\u0204-\u0207\u0228\u0229\u1d31\u1d49\u1e18-\u1e1b\u1eb8-\u1ebd\u2091\u2121\u212f\u2130\u2147\u24a0\u24ba\u24d4\u3250\u32cd\u32ce\uff25\uff45]',
    'F': '[Ff\u1da0\u1e1e\u1e1f\u2109\u2131\u213b\u24a1\u24bb\u24d5\u338a-\u338c\u3399\ufb00-\ufb04\uff26\uff46]',
    'G': '[Gg\u011c-\u0123\u01e6\u01e7\u01f4\u01f5\u1d33\u1d4d\u1e20\u1e21\u210a\u24a2\u24bc\u24d6\u32cc\u32cd\u3387\u338d-\u338f\u3393\u33ac\u33c6\u33c9\u33d2\u33ff\uff27\uff47]',
    'H': '[Hh\u0124\u0125\u021e\u021f\u02b0\u1d34\u1e22-\u1e2b\u1e96\u210b-\u210e\u24a3\u24bd\u24d7\u32cc\u3371\u3390-\u3394\u33ca\u33cb\u33d7\uff28\uff48]',
    'I': '[Ii\xcc-\xcf\xec-\xef\u0128-\u0130\u0132\u0133\u01cf\u01d0\u0208-\u020b\u1d35\u1d62\u1e2c\u1e2d\u1ec8-\u1ecb\u2071\u2110\u2111\u2139\u2148\u2160-\u2163\u2165-\u2168\u216a\u216b\u2170-\u2173\u2175-\u2178\u217a\u217b\u24a4\u24be\u24d8\u337a\u33cc\u33d5\ufb01\ufb03\uff29\uff49]',
    'J': '[Jj\u0132-\u0135\u01c7-\u01cc\u01f0\u02b2\u1d36\u2149\u24a5\u24bf\u24d9\u2c7c\uff2a\uff4a]',
    'K': '[Kk\u0136\u0137\u01e8\u01e9\u1d37\u1d4f\u1e30-\u1e35\u212a\u24a6\u24c0\u24da\u3384\u3385\u3389\u338f\u3391\u3398\u339e\u33a2\u33a6\u33aa\u33b8\u33be\u33c0\u33c6\u33cd-\u33cf\uff2b\uff4b]',
    'L': '[Ll\u0139-\u0140\u01c7-\u01c9\u02e1\u1d38\u1e36\u1e37\u1e3a-\u1e3d\u2112\u2113\u2121\u216c\u217c\u24a7\u24c1\u24db\u32cf\u3388\u3389\u33d0-\u33d3\u33d5\u33d6\u33ff\ufb02\ufb04\uff2c\uff4c]',
    'M': '[Mm\u1d39\u1d50\u1e3e-\u1e43\u2120\u2122\u2133\u216f\u217f\u24a8\u24c2\u24dc\u3377-\u3379\u3383\u3386\u338e\u3392\u3396\u3399-\u33a8\u33ab\u33b3\u33b7\u33b9\u33bd\u33bf\u33c1\u33c2\u33ce\u33d0\u33d4-\u33d6\u33d8\u33d9\u33de\u33df\uff2d\uff4d]',
    'N': '[Nn\xd1\xf1\u0143-\u0149\u01ca-\u01cc\u01f8\u01f9\u1d3a\u1e44-\u1e4b\u207f\u2115\u2116\u24a9\u24c3\u24dd\u3381\u338b\u339a\u33b1\u33b5\u33bb\u33cc\u33d1\uff2e\uff4e]',
    'O': '[Oo\xba\xd2-\xd6\xf2-\xf6\u014c-\u0151\u01a0\u01a1\u01d1\u01d2\u01ea\u01eb\u020c-\u020f\u022e\u022f\u1d3c\u1d52\u1ecc-\u1ecf\u2092\u2105\u2116\u2134\u24aa\u24c4\u24de\u3375\u33c7\u33d2\u33d6\uff2f\uff4f]',
    'P': '[Pp\u1d3e\u1d56\u1e54-\u1e57\u2119\u24ab\u24c5\u24df\u3250\u3371\u3376\u3380\u338a\u33a9-\u33ac\u33b0\u33b4\u33ba\u33cb\u33d7-\u33da\uff30\uff50]',
    'Q': '[Qq\u211a\u24ac\u24c6\u24e0\u33c3\uff31\uff51]',
    'R': '[Rr\u0154-\u0159\u0210-\u0213\u02b3\u1d3f\u1d63\u1e58-\u1e5b\u1e5e\u1e5f\u20a8\u211b-\u211d\u24ad\u24c7\u24e1\u32cd\u3374\u33ad-\u33af\u33da\u33db\uff32\uff52]',
    'S': '[Ss\u015a-\u0161\u017f\u0218\u0219\u02e2\u1e60-\u1e63\u20a8\u2101\u2120\u24ae\u24c8\u24e2\u33a7\u33a8\u33ae-\u33b3\u33db\u33dc\ufb06\uff33\uff53]',
    'T': '[Tt\u0162-\u0165\u021a\u021b\u1d40\u1d57\u1e6a-\u1e71\u1e97\u2121\u2122\u24af\u24c9\u24e3\u3250\u32cf\u3394\u33cf\ufb05\ufb06\uff34\uff54]',
    'U': '[Uu\xd9-\xdc\xf9-\xfc\u0168-\u0173\u01af\u01b0\u01d3\u01d4\u0214-\u0217\u1d41\u1d58\u1d64\u1e72-\u1e77\u1ee4-\u1ee7\u2106\u24b0\u24ca\u24e4\u3373\u337a\uff35\uff55]',
    'V': '[Vv\u1d5b\u1d65\u1e7c-\u1e7f\u2163-\u2167\u2173-\u2177\u24b1\u24cb\u24e5\u2c7d\u32ce\u3375\u33b4-\u33b9\u33dc\u33de\uff36\uff56]',
    'W': '[Ww\u0174\u0175\u02b7\u1d42\u1e80-\u1e89\u1e98\u24b2\u24cc\u24e6\u33ba-\u33bf\u33dd\uff37\uff57]',
    'X': '[Xx\u02e3\u1e8a-\u1e8d\u2093\u213b\u2168-\u216b\u2178-\u217b\u24b3\u24cd\u24e7\u33d3\uff38\uff58]',
    'Y': '[Yy\xdd\xfd\xff\u0176-\u0178\u0232\u0233\u02b8\u1e8e\u1e8f\u1e99\u1ef2-\u1ef9\u24b4\u24ce\u24e8\u33c9\uff39\uff59]',
    'Z': '[Zz\u0179-\u017e\u01f1-\u01f3\u1dbb\u1e90-\u1e95\u2124\u2128\u24b5\u24cf\u24e9\u3390-\u3394\uff3a\uff5a]'
};

Annabellannabella

So you're saying that there's no built-in structure to Unicode where I could reduce an accented character to it's base components using bitmasks or anything like that? Because this kind of var accented data is large and potentially unmaintainable. – Savick

You could generate it from an official source: ftp.unicode.org/Public/UNIDATA/UnicodeData.txt . You just need to go trough each line, and look at the characters in the composition field. – Annabellannabella

Was listing all characters done for clarity? Why not replace, for example, '[Zz\u0179\u017a\u017b\u017c\u017d\u017e\u01f1\u01f2\u01f3\u1dbb\u1e90\u1e91\u1e92\u1e93\u1e94\u1e95\u2124\u2128\u24b5\u24cf\u24e9\u3390\u3391\u3392\u3393\u3394\uff3a\uff5a]' with functionally identical - '[Zz\u0179-\u017e\u01f1-\u01f3\u1dbb\u1e90-\u1e95\u2124\u2128\u24b5\u24cf\u24e9\u3390-\u3394\uff3a\uff5a]'? – Schematism

It was generated directly from UnicodeData.txt. I thought it was too much work to write a sequence detector function. Fixed now though. – Annabellannabella

Man, this is awesome! The code inspired me to write a lenient jQuery highlight plugin: http://www.frightanic.com/projects/lenient-jquery-highlight-plugin-javascript/ – Pliam

Belatedly accepted; though I do like the diacritic removal answer below. – Savick

Answer 2

A more complete version with case sensitive support, ligatures and whatnot. Original source at: http://lehelk.com/2011/05/06/script-to-remove-diacritics/

var defaultDiacriticsRemovalMap = [
    {'base':'A', 'letters':/[\u0041\u24B6\uFF21\u00C0\u00C1\u00C2\u1EA6\u1EA4\u1EAA\u1EA8\u00C3\u0100\u0102\u1EB0\u1EAE\u1EB4\u1EB2\u0226\u01E0\u00C4\u01DE\u1EA2\u00C5\u01FA\u01CD\u0200\u0202\u1EA0\u1EAC\u1EB6\u1E00\u0104\u023A\u2C6F]/g},
    {'base':'AA','letters':/[\uA732]/g},
    {'base':'AE','letters':/[\u00C6\u01FC\u01E2]/g},
    {'base':'AO','letters':/[\uA734]/g},
    {'base':'AU','letters':/[\uA736]/g},
    {'base':'AV','letters':/[\uA738\uA73A]/g},
    {'base':'AY','letters':/[\uA73C]/g},
    {'base':'B', 'letters':/[\u0042\u24B7\uFF22\u1E02\u1E04\u1E06\u0243\u0182\u0181]/g},
    {'base':'C', 'letters':/[\u0043\u24B8\uFF23\u0106\u0108\u010A\u010C\u00C7\u1E08\u0187\u023B\uA73E]/g},
    {'base':'D', 'letters':/[\u0044\u24B9\uFF24\u1E0A\u010E\u1E0C\u1E10\u1E12\u1E0E\u0110\u018B\u018A\u0189\uA779]/g},
    {'base':'DZ','letters':/[\u01F1\u01C4]/g},
    {'base':'Dz','letters':/[\u01F2\u01C5]/g},
    {'base':'E', 'letters':/[\u0045\u24BA\uFF25\u00C8\u00C9\u00CA\u1EC0\u1EBE\u1EC4\u1EC2\u1EBC\u0112\u1E14\u1E16\u0114\u0116\u00CB\u1EBA\u011A\u0204\u0206\u1EB8\u1EC6\u0228\u1E1C\u0118\u1E18\u1E1A\u0190\u018E]/g},
    {'base':'F', 'letters':/[\u0046\u24BB\uFF26\u1E1E\u0191\uA77B]/g},
    {'base':'G', 'letters':/[\u0047\u24BC\uFF27\u01F4\u011C\u1E20\u011E\u0120\u01E6\u0122\u01E4\u0193\uA7A0\uA77D\uA77E]/g},
    {'base':'H', 'letters':/[\u0048\u24BD\uFF28\u0124\u1E22\u1E26\u021E\u1E24\u1E28\u1E2A\u0126\u2C67\u2C75\uA78D]/g},
    {'base':'I', 'letters':/[\u0049\u24BE\uFF29\u00CC\u00CD\u00CE\u0128\u012A\u012C\u0130\u00CF\u1E2E\u1EC8\u01CF\u0208\u020A\u1ECA\u012E\u1E2C\u0197]/g},
    {'base':'J', 'letters':/[\u004A\u24BF\uFF2A\u0134\u0248]/g},
    {'base':'K', 'letters':/[\u004B\u24C0\uFF2B\u1E30\u01E8\u1E32\u0136\u1E34\u0198\u2C69\uA740\uA742\uA744\uA7A2]/g},
    {'base':'L', 'letters':/[\u004C\u24C1\uFF2C\u013F\u0139\u013D\u1E36\u1E38\u013B\u1E3C\u1E3A\u0141\u023D\u2C62\u2C60\uA748\uA746\uA780]/g},
    {'base':'LJ','letters':/[\u01C7]/g},
    {'base':'Lj','letters':/[\u01C8]/g},
    {'base':'M', 'letters':/[\u004D\u24C2\uFF2D\u1E3E\u1E40\u1E42\u2C6E\u019C]/g},
    {'base':'N', 'letters':/[\u004E\u24C3\uFF2E\u01F8\u0143\u00D1\u1E44\u0147\u1E46\u0145\u1E4A\u1E48\u0220\u019D\uA790\uA7A4]/g},
    {'base':'NJ','letters':/[\u01CA]/g},
    {'base':'Nj','letters':/[\u01CB]/g},
    {'base':'O', 'letters':/[\u004F\u24C4\uFF2F\u00D2\u00D3\u00D4\u1ED2\u1ED0\u1ED6\u1ED4\u00D5\u1E4C\u022C\u1E4E\u014C\u1E50\u1E52\u014E\u022E\u0230\u00D6\u022A\u1ECE\u0150\u01D1\u020C\u020E\u01A0\u1EDC\u1EDA\u1EE0\u1EDE\u1EE2\u1ECC\u1ED8\u01EA\u01EC\u00D8\u01FE\u0186\u019F\uA74A\uA74C]/g},
    {'base':'OI','letters':/[\u01A2]/g},
    {'base':'OO','letters':/[\uA74E]/g},
    {'base':'OU','letters':/[\u0222]/g},
    {'base':'P', 'letters':/[\u0050\u24C5\uFF30\u1E54\u1E56\u01A4\u2C63\uA750\uA752\uA754]/g},
    {'base':'Q', 'letters':/[\u0051\u24C6\uFF31\uA756\uA758\u024A]/g},
    {'base':'R', 'letters':/[\u0052\u24C7\uFF32\u0154\u1E58\u0158\u0210\u0212\u1E5A\u1E5C\u0156\u1E5E\u024C\u2C64\uA75A\uA7A6\uA782]/g},
    {'base':'S', 'letters':/[\u0053\u24C8\uFF33\u1E9E\u015A\u1E64\u015C\u1E60\u0160\u1E66\u1E62\u1E68\u0218\u015E\u2C7E\uA7A8\uA784]/g},
    {'base':'T', 'letters':/[\u0054\u24C9\uFF34\u1E6A\u0164\u1E6C\u021A\u0162\u1E70\u1E6E\u0166\u01AC\u01AE\u023E\uA786]/g},
    {'base':'TZ','letters':/[\uA728]/g},
    {'base':'U', 'letters':/[\u0055\u24CA\uFF35\u00D9\u00DA\u00DB\u0168\u1E78\u016A\u1E7A\u016C\u00DC\u01DB\u01D7\u01D5\u01D9\u1EE6\u016E\u0170\u01D3\u0214\u0216\u01AF\u1EEA\u1EE8\u1EEE\u1EEC\u1EF0\u1EE4\u1E72\u0172\u1E76\u1E74\u0244]/g},
    {'base':'V', 'letters':/[\u0056\u24CB\uFF36\u1E7C\u1E7E\u01B2\uA75E\u0245]/g},
    {'base':'VY','letters':/[\uA760]/g},
    {'base':'W', 'letters':/[\u0057\u24CC\uFF37\u1E80\u1E82\u0174\u1E86\u1E84\u1E88\u2C72]/g},
    {'base':'X', 'letters':/[\u0058\u24CD\uFF38\u1E8A\u1E8C]/g},
    {'base':'Y', 'letters':/[\u0059\u24CE\uFF39\u1EF2\u00DD\u0176\u1EF8\u0232\u1E8E\u0178\u1EF6\u1EF4\u01B3\u024E\u1EFE]/g},
    {'base':'Z', 'letters':/[\u005A\u24CF\uFF3A\u0179\u1E90\u017B\u017D\u1E92\u1E94\u01B5\u0224\u2C7F\u2C6B\uA762]/g},
    {'base':'a', 'letters':/[\u0061\u24D0\uFF41\u1E9A\u00E0\u00E1\u00E2\u1EA7\u1EA5\u1EAB\u1EA9\u00E3\u0101\u0103\u1EB1\u1EAF\u1EB5\u1EB3\u0227\u01E1\u00E4\u01DF\u1EA3\u00E5\u01FB\u01CE\u0201\u0203\u1EA1\u1EAD\u1EB7\u1E01\u0105\u2C65\u0250]/g},
    {'base':'aa','letters':/[\uA733]/g},
    {'base':'ae','letters':/[\u00E6\u01FD\u01E3]/g},
    {'base':'ao','letters':/[\uA735]/g},
    {'base':'au','letters':/[\uA737]/g},
    {'base':'av','letters':/[\uA739\uA73B]/g},
    {'base':'ay','letters':/[\uA73D]/g},
    {'base':'b', 'letters':/[\u0062\u24D1\uFF42\u1E03\u1E05\u1E07\u0180\u0183\u0253]/g},
    {'base':'c', 'letters':/[\u0063\u24D2\uFF43\u0107\u0109\u010B\u010D\u00E7\u1E09\u0188\u023C\uA73F\u2184]/g},
    {'base':'d', 'letters':/[\u0064\u24D3\uFF44\u1E0B\u010F\u1E0D\u1E11\u1E13\u1E0F\u0111\u018C\u0256\u0257\uA77A]/g},
    {'base':'dz','letters':/[\u01F3\u01C6]/g},
    {'base':'e', 'letters':/[\u0065\u24D4\uFF45\u00E8\u00E9\u00EA\u1EC1\u1EBF\u1EC5\u1EC3\u1EBD\u0113\u1E15\u1E17\u0115\u0117\u00EB\u1EBB\u011B\u0205\u0207\u1EB9\u1EC7\u0229\u1E1D\u0119\u1E19\u1E1B\u0247\u025B\u01DD]/g},
    {'base':'f', 'letters':/[\u0066\u24D5\uFF46\u1E1F\u0192\uA77C]/g},
    {'base':'g', 'letters':/[\u0067\u24D6\uFF47\u01F5\u011D\u1E21\u011F\u0121\u01E7\u0123\u01E5\u0260\uA7A1\u1D79\uA77F]/g},
    {'base':'h', 'letters':/[\u0068\u24D7\uFF48\u0125\u1E23\u1E27\u021F\u1E25\u1E29\u1E2B\u1E96\u0127\u2C68\u2C76\u0265]/g},
    {'base':'hv','letters':/[\u0195]/g},
    {'base':'i', 'letters':/[\u0069\u24D8\uFF49\u00EC\u00ED\u00EE\u0129\u012B\u012D\u00EF\u1E2F\u1EC9\u01D0\u0209\u020B\u1ECB\u012F\u1E2D\u0268\u0131]/g},
    {'base':'j', 'letters':/[\u006A\u24D9\uFF4A\u0135\u01F0\u0249]/g},
    {'base':'k', 'letters':/[\u006B\u24DA\uFF4B\u1E31\u01E9\u1E33\u0137\u1E35\u0199\u2C6A\uA741\uA743\uA745\uA7A3]/g},
    {'base':'l', 'letters':/[\u006C\u24DB\uFF4C\u0140\u013A\u013E\u1E37\u1E39\u013C\u1E3D\u1E3B\u017F\u0142\u019A\u026B\u2C61\uA749\uA781\uA747]/g},
    {'base':'lj','letters':/[\u01C9]/g},
    {'base':'m', 'letters':/[\u006D\u24DC\uFF4D\u1E3F\u1E41\u1E43\u0271\u026F]/g},
    {'base':'n', 'letters':/[\u006E\u24DD\uFF4E\u01F9\u0144\u00F1\u1E45\u0148\u1E47\u0146\u1E4B\u1E49\u019E\u0272\u0149\uA791\uA7A5]/g},
    {'base':'nj','letters':/[\u01CC]/g},
    {'base':'o', 'letters':/[\u006F\u24DE\uFF4F\u00F2\u00F3\u00F4\u1ED3\u1ED1\u1ED7\u1ED5\u00F5\u1E4D\u022D\u1E4F\u014D\u1E51\u1E53\u014F\u022F\u0231\u00F6\u022B\u1ECF\u0151\u01D2\u020D\u020F\u01A1\u1EDD\u1EDB\u1EE1\u1EDF\u1EE3\u1ECD\u1ED9\u01EB\u01ED\u00F8\u01FF\u0254\uA74B\uA74D\u0275]/g},
    {'base':'oi','letters':/[\u01A3]/g},
    {'base':'ou','letters':/[\u0223]/g},
    {'base':'oo','letters':/[\uA74F]/g},
    {'base':'p','letters':/[\u0070\u24DF\uFF50\u1E55\u1E57\u01A5\u1D7D\uA751\uA753\uA755]/g},
    {'base':'q','letters':/[\u0071\u24E0\uFF51\u024B\uA757\uA759]/g},
    {'base':'r','letters':/[\u0072\u24E1\uFF52\u0155\u1E59\u0159\u0211\u0213\u1E5B\u1E5D\u0157\u1E5F\u024D\u027D\uA75B\uA7A7\uA783]/g},
    {'base':'s','letters':/[\u0073\u24E2\uFF53\u00DF\u015B\u1E65\u015D\u1E61\u0161\u1E67\u1E63\u1E69\u0219\u015F\u023F\uA7A9\uA785\u1E9B]/g},
    {'base':'t','letters':/[\u0074\u24E3\uFF54\u1E6B\u1E97\u0165\u1E6D\u021B\u0163\u1E71\u1E6F\u0167\u01AD\u0288\u2C66\uA787]/g},
    {'base':'tz','letters':/[\uA729]/g},
    {'base':'u','letters':/[\u0075\u24E4\uFF55\u00F9\u00FA\u00FB\u0169\u1E79\u016B\u1E7B\u016D\u00FC\u01DC\u01D8\u01D6\u01DA\u1EE7\u016F\u0171\u01D4\u0215\u0217\u01B0\u1EEB\u1EE9\u1EEF\u1EED\u1EF1\u1EE5\u1E73\u0173\u1E77\u1E75\u0289]/g},
    {'base':'v','letters':/[\u0076\u24E5\uFF56\u1E7D\u1E7F\u028B\uA75F\u028C]/g},
    {'base':'vy','letters':/[\uA761]/g},
    {'base':'w','letters':/[\u0077\u24E6\uFF57\u1E81\u1E83\u0175\u1E87\u1E85\u1E98\u1E89\u2C73]/g},
    {'base':'x','letters':/[\u0078\u24E7\uFF58\u1E8B\u1E8D]/g},
    {'base':'y','letters':/[\u0079\u24E8\uFF59\u1EF3\u00FD\u0177\u1EF9\u0233\u1E8F\u00FF\u1EF7\u1E99\u1EF5\u01B4\u024F\u1EFF]/g},
    {'base':'z','letters':/[\u007A\u24E9\uFF5A\u017A\u1E91\u017C\u017E\u1E93\u1E95\u01B6\u0225\u0240\u2C6C\uA763]/g}
];
var changes;
function removeDiacritics (str) {
    if(!changes) {
        changes = defaultDiacriticsRemovalMap;
    }
    for(var i=0; i<changes.length; i++) {
        str = str.replace(changes[i].letters, changes[i].base);
    }
    return str;
}

Pollaiuolo

Great, but what is the function of changes var? Thankyou – Chavers

about str.replace "This method does not change the original string." which means that the "changes" var is not important, since you could have it directly in the scope of removeDiacritics(str) i updated your code @Pollaiuolo – Talley

Does this also do Eszett (ß) → "ss", ash (Æ, æ) → "ae", thorn (Þ, þ) → "th", and eth (Ð, ð) → "th"? Because if someone is searching for "Æðelstan Straße" you'd want to accept "Aethelstan Strasse" as input. – Unsecured