diff --git a/.circleci/config.yml b/.circleci/config.yml
new file mode 100644
index 0000000..ab5f676
--- /dev/null
+++ b/.circleci/config.yml
@@ -0,0 +1,31 @@
+# Javascript Node CircleCI 2.0 configuration file
+#
+# Check https://circleci.com/docs/2.0/language-javascript/ for more details
+#
+version: 2
+
+defaults: &defaults
+  working_directory: ~/normalize-diacritics
+  docker:
+    - image: circleci/python:2-node
+
+jobs:
+  test:
+    steps:
+      - checkout
+      - run:
+          name: Install Deno
+          command: |
+            - curl -fsSL https://deno.land/x/install/install.sh | sh
+            - export PATH=$HOME/.deno/bin:$PATH
+      - run:
+          name: Versions
+          command: deno -v && which deno && pwd
+      - run:
+          name: Test
+          command: deno ./mod_test.ts
+
+workflows:
+  version: 2
+  jobs:
+    - test
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index ceb4819..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,18 +0,0 @@
-language: python
-
-matrix:
-  include:
-    - os: linux
-      name: linux:deno_testing
-    # - os: windows
-    #   name: windows:deno_testing
-
-# before_install:
-
-install:
-  - curl -L https://deno.land/x/install/install.py | python
-  - export PATH=$HOME/.deno/bin:$PATH
-
-script:
-  - deno -v
-  - deno test/index.spec.ts
diff --git a/README.md b/README.md
index c476da3..2edc33d 100644
--- a/README.md
+++ b/README.md
@@ -10,13 +10,18 @@
 [![Deno Version][deno-version-badge]][deno-version-url]
 [![MIT License][mit-license-badge]][mit-license-url]
 
-[![jsDelivr downloads][jsdelivr-badge]][jsdelivr-url]
+[![CircleCI][circleci-badge]][circleci-url]
 
-[![Build Status][travis-badge]][travis-url]
+> Simple [deno][deno-url] module to remove any accents/ diacritics found in a string.
 
-> Simple [deno][deno-url] library to remove any accents/ diacritics found in a string.
+## Table of contents <!-- omit in toc -->
 
-## Table of contents
+- [Pre-requisite](#pre-requisite)
+- [Usage](#usage)
+- [API Reference](#api-reference)
+  - [normalize([input])](#normalizeinput)
+  - [normalizeSync([input])](#normalizesyncinput)
+- [License](#license)
 
 ## Pre-requisite
 
@@ -26,12 +31,10 @@
 
 ```ts
 /** Import from GH via `denopkg` */
-import { normalize } from 'https://denopkg.com/motss/normalize-diacritics@v1.0.1-deno/index.ts';
-/** Or, import from a CDN such as `jsdelivr` */
-// import { normalize } from 'https://cdn.jsdelivr.net/gh/motss/normalize-diacritics@1.0.1-deno/index.ts';
+import { normalize } from "https://denopkg.com/motss/normalize-diacritics@deno/mod.ts";
 
 (async () => {
-  const str = 'söme stüff with áccènts';
+  const str = "söme stüff with áccènts";
 
   await normalize(str); // 'some stuff with accents'
 })();
@@ -67,19 +70,15 @@ This methods works the same as `normalize([input])` except that this is the sync
 [promise-mdn-url]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise
 
 <!-- Badges -->
-[version-badge]: https://flat.badgen.net/badge/version/v1.0.1-deno/blue?icon=github
-[deno-version-badge]: https://flat.badgen.net/badge/deno/v0.2.6/blue?icon=github
+[version-badge]: https://flat.badgen.net/badge/branch/deno/blue?icon=github
+[deno-version-badge]: https://flat.badgen.net/github/release/denoland/deno/stable?icon=github
 [mit-license-badge]: https://flat.badgen.net/npm/license/normalize-diacritics
 
-[jsdelivr-badge]: https://data.jsdelivr.com/v1/package/gh/motss/normalize-diacritics/badge
-
-[travis-badge]: https://flat.badgen.net/travis/motss/normalize-diacritics/deno
+[circleci-badge]: https://flat.badgen.net/circleci/github/motss/normalize-diacritics/deno?icon=circleci
 
 <!-- Links -->
 [version-url]: https://github.com/motss/normalize-diacritics/tree/deno
 [deno-version-url]: https://github.com/denoland/deno
 [mit-license-url]: https://github.com/motss/normalize-diacritics/blob/deno/LICENSE
 
-[jsdelivr-url]: https://www.jsdelivr.com/package/gh/motss/normalize-diacritics?version=1.0.1-deno
-
-[travis-url]: https://travis-ci.org/motss/normalize-diacritics
+[circleci-url]: https://circleci.com/gh/motss/normalize-diacritics/tree/deno
diff --git a/helpers.ts b/helpers.ts
new file mode 100644
index 0000000..5fa0ad5
--- /dev/null
+++ b/helpers.ts
@@ -0,0 +1,264 @@
+export interface Diacritics {
+  letter: string;
+  diacritics: RegExp;
+}
+
+/**
+ * NOTE: A more complete list of diacritics are from:-
+ *   1. - https://bit.ly/2Fc0HB1
+ *   2. https://bit.ly/2ComN2J
+ */
+// tslint:disable:max-line-length
+export const diacritics: Diacritics[] = [
+  { letter: " ", diacritics: /[\u00A0]/g },
+  { letter: "0", diacritics: /[\u07C0]/g },
+  {
+    letter: "A",
+    diacritics: /[\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
+  },
+  { letter: "AA", diacritics: /[\uA732]/g },
+  { letter: "AE", diacritics: /[\u00C6\u01FC\u01E2]/g },
+  { letter: "AO", diacritics: /[\uA734]/g },
+  { letter: "AU", diacritics: /[\uA736]/g },
+  { letter: "AV", diacritics: /[\uA738\uA73A]/g },
+  { letter: "AY", diacritics: /[\uA73C]/g },
+  {
+    letter: "B",
+    diacritics: /[\u0042\u24B7\uFF22\u1E02\u1E04\u1E06\u0243\u0182\u0181]/g
+  },
+  {
+    letter: "C",
+    diacritics: /[\u0043\u24B8\uFF23\u0106\u0108\u010A\u010C\u00C7\u1E08\u0187\u023B\uA73E]/g
+  },
+  {
+    letter: "D",
+    diacritics: /[\u0044\u24B9\uFF24\u1E0A\u010E\u1E0C\u1E10\u1E12\u1E0E\u0110\u018B\u018A\u0189\uA779]/g
+  },
+  { letter: "Dh", diacritics: /[\u00D0]/g },
+  { letter: "DZ", diacritics: /[\u01F1\u01C4]/g },
+  { letter: "Dz", diacritics: /[\u01F2\u01C5]/g },
+  {
+    letter: "E",
+    diacritics: /[\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
+  },
+  { letter: "F", diacritics: /[\u0046\u24BB\uFF26\u1E1E\u0191\uA77B]/g },
+  {
+    letter: "G",
+    diacritics: /[\u0047\u24BC\uFF27\u01F4\u011C\u1E20\u011E\u0120\u01E6\u0122\u01E4\u0193\uA7A0\uA77D\uA77E]/g
+  },
+  {
+    letter: "H",
+    diacritics: /[\u0048\u24BD\uFF28\u0124\u1E22\u1E26\u021E\u1E24\u1E28\u1E2A\u0126\u2C67\u2C75\uA78D]/g
+  },
+  {
+    letter: "I",
+    diacritics: /[\u0049\u24BE\uFF29\u00CC\u00CD\u00CE\u0128\u012A\u012C\u0130\u00CF\u1E2E\u1EC8\u01CF\u0208\u020A\u1ECA\u012E\u1E2C\u0197]/g
+  },
+  { letter: "J", diacritics: /[\u004A\u24BF\uFF2A\u0134\u0248]/g },
+  {
+    letter: "K",
+    diacritics: /[\u004B\u24C0\uFF2B\u1E30\u01E8\u1E32\u0136\u1E34\u0198\u2C69\uA740\uA742\uA744\uA7A2]/g
+  },
+  {
+    letter: "L",
+    diacritics: /[\u004C\u24C1\uFF2C\u013F\u0139\u013D\u1E36\u1E38\u013B\u1E3C\u1E3A\u0141\u023D\u2C62\u2C60\uA748\uA746\uA780]/g
+  },
+  { letter: "LJ", diacritics: /[\u01C7]/g },
+  { letter: "Lj", diacritics: /[\u01C8]/g },
+  {
+    letter: "M",
+    diacritics: /[\u004D\u24C2\uFF2D\u1E3E\u1E40\u1E42\u2C6E\u019C]/g
+  },
+  {
+    letter: "N",
+    diacritics: /[\u004E\u24C3\uFF2E\u01F8\u0143\u00D1\u1E44\u0147\u1E46\u0145\u1E4A\u1E48\u0220\u019D\uA790\uA7A4]/g
+  },
+  { letter: "NJ", diacritics: /[\u01CA]/g },
+  { letter: "Nj", diacritics: /[\u01CB]/g },
+  {
+    letter: "O",
+    diacritics: /[\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
+  },
+  { letter: "OE", diacritics: /[\u0152]/g },
+  { letter: "OI", diacritics: /[\u01A2]/g },
+  { letter: "OO", diacritics: /[\uA74E]/g },
+  { letter: "OU", diacritics: /[\u0222]/g },
+  {
+    letter: "P",
+    diacritics: /[\u0050\u24C5\uFF30\u1E54\u1E56\u01A4\u2C63\uA750\uA752\uA754]/g
+  },
+  { letter: "Q", diacritics: /[\u0051\u24C6\uFF31\uA756\uA758\u024A]/g },
+  {
+    letter: "R",
+    diacritics: /[\u0052\u24C7\uFF32\u0154\u1E58\u0158\u0210\u0212\u1E5A\u1E5C\u0156\u1E5E\u024C\u2C64\uA75A\uA7A6\uA782]/g
+  },
+  {
+    letter: "S",
+    diacritics: /[\u0053\u24C8\uFF33\u1E9E\u015A\u1E64\u015C\u1E60\u0160\u1E66\u1E62\u1E68\u0218\u015E\u2C7E\uA7A8\uA784]/g
+  },
+  {
+    letter: "T",
+    diacritics: /[\u0054\u24C9\uFF34\u1E6A\u0164\u1E6C\u021A\u0162\u1E70\u1E6E\u0166\u01AC\u01AE\u023E\uA786]/g
+  },
+  { letter: "Th", diacritics: /[\u00DE]/g },
+  { letter: "TZ", diacritics: /[\uA728]/g },
+  {
+    letter: "U",
+    diacritics: /[\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
+  },
+  {
+    letter: "V",
+    diacritics: /[\u0056\u24CB\uFF36\u1E7C\u1E7E\u01B2\uA75E\u0245]/g
+  },
+  { letter: "VY", diacritics: /[\uA760]/g },
+  {
+    letter: "W",
+    diacritics: /[\u0057\u24CC\uFF37\u1E80\u1E82\u0174\u1E86\u1E84\u1E88\u2C72]/g
+  },
+  { letter: "X", diacritics: /[\u0058\u24CD\uFF38\u1E8A\u1E8C]/g },
+  {
+    letter: "Y",
+    diacritics: /[\u0059\u24CE\uFF39\u1EF2\u00DD\u0176\u1EF8\u0232\u1E8E\u0178\u1EF6\u1EF4\u01B3\u024E\u1EFE]/g
+  },
+  {
+    letter: "Z",
+    diacritics: /[\u005A\u24CF\uFF3A\u0179\u1E90\u017B\u017D\u1E92\u1E94\u01B5\u0224\u2C7F\u2C6B\uA762]/g
+  },
+  {
+    letter: "a",
+    diacritics: /[\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
+  },
+  { letter: "aa", diacritics: /[\uA733]/g },
+  { letter: "ae", diacritics: /[\u00E6\u01FD\u01E3]/g },
+  { letter: "ao", diacritics: /[\uA735]/g },
+  { letter: "au", diacritics: /[\uA737]/g },
+  { letter: "av", diacritics: /[\uA739\uA73B]/g },
+  { letter: "ay", diacritics: /[\uA73D]/g },
+  {
+    letter: "b",
+    diacritics: /[\u0062\u24D1\uFF42\u1E03\u1E05\u1E07\u0180\u0183\u0253]/g
+  },
+  {
+    letter: "c",
+    diacritics: /[\u0063\u24D2\uFF43\u0107\u0109\u010B\u010D\u00E7\u1E09\u0188\u023C\uA73F\u2184]/g
+  },
+  {
+    letter: "d",
+    diacritics: /[\u0064\u24D3\uFF44\u1E0B\u010F\u1E0D\u1E11\u1E13\u1E0F\u0111\u018C\u0256\u0257\uA77A]/g
+  },
+  { letter: "dh", diacritics: /[\u00F0]/g },
+  { letter: "dz", diacritics: /[\u01F3\u01C6]/g },
+  {
+    letter: "e",
+    diacritics: /[\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
+  },
+  { letter: "f", diacritics: /[\u0066\u24D5\uFF46\u1E1F\u0192\uA77C]/g },
+  { letter: "ff", diacritics: /[\uFB00]/g },
+  { letter: "fi", diacritics: /[\uFB01]/g },
+  { letter: "fl", diacritics: /[\uFB02]/g },
+  { letter: "ffi", diacritics: /[\uFB03]/g },
+  { letter: "ffl", diacritics: /[\uFB04]/g },
+  {
+    letter: "g",
+    diacritics: /[\u0067\u24D6\uFF47\u01F5\u011D\u1E21\u011F\u0121\u01E7\u0123\u01E5\u0260\uA7A1\u1D79\uA77F]/g
+  },
+  {
+    letter: "h",
+    diacritics: /[\u0068\u24D7\uFF48\u0125\u1E23\u1E27\u021F\u1E25\u1E29\u1E2B\u1E96\u0127\u2C68\u2C76\u0265]/g
+  },
+  { letter: "hv", diacritics: /[\u0195]/g },
+  {
+    letter: "i",
+    diacritics: /[\u0069\u24D8\uFF49\u00EC\u00ED\u00EE\u0129\u012B\u012D\u00EF\u1E2F\u1EC9\u01D0\u0209\u020B\u1ECB\u012F\u1E2D\u0268\u0131]/g
+  },
+  { letter: "j", diacritics: /[\u006A\u24D9\uFF4A\u0135\u01F0\u0249]/g },
+  {
+    letter: "k",
+    diacritics: /[\u006B\u24DA\uFF4B\u1E31\u01E9\u1E33\u0137\u1E35\u0199\u2C6A\uA741\uA743\uA745\uA7A3]/g
+  },
+  {
+    letter: "l",
+    diacritics: /[\u006C\u24DB\uFF4C\u0140\u013A\u013E\u1E37\u1E39\u013C\u1E3D\u1E3B\u017F\u0142\u019A\u026B\u2C61\uA749\uA781\uA747]/g
+  },
+  { letter: "lj", diacritics: /[\u01C9]/g },
+  {
+    letter: "m",
+    diacritics: /[\u006D\u24DC\uFF4D\u1E3F\u1E41\u1E43\u0271\u026F]/g
+  },
+  {
+    letter: "n",
+    diacritics: /[\u006E\u24DD\uFF4E\u01F9\u0144\u00F1\u1E45\u0148\u1E47\u0146\u1E4B\u1E49\u019E\u0272\u0149\uA791\uA7A5]/g
+  },
+  { letter: "nj", diacritics: /[\u01CC]/g },
+  {
+    letter: "o",
+    diacritics: /[\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
+  },
+  { letter: "oe", diacritics: /[\u0153]/g },
+  { letter: "oi", diacritics: /[\u01A3]/g },
+  { letter: "ou", diacritics: /[\u0223]/g },
+  { letter: "oo", diacritics: /[\uA74F]/g },
+  {
+    letter: "p",
+    diacritics: /[\u0070\u24DF\uFF50\u1E55\u1E57\u01A5\u1D7D\uA751\uA753\uA755]/g
+  },
+  { letter: "q", diacritics: /[\u0071\u24E0\uFF51\u024B\uA757\uA759]/g },
+  {
+    letter: "r",
+    diacritics: /[\u0072\u24E1\uFF52\u0155\u1E59\u0159\u0211\u0213\u1E5B\u1E5D\u0157\u1E5F\u024D\u027D\uA75B\uA7A7\uA783]/g
+  },
+  {
+    letter: "s",
+    diacritics: /[\u0073\u24E2\uFF53\u00DF\u015B\u1E65\u015D\u1E61\u0161\u1E67\u1E63\u1E69\u0219\u015F\u023F\uA7A9\uA785\u1E9B]/g
+  },
+  { letter: "ss", diacritics: /[\xDF]/g },
+  {
+    letter: "t",
+    diacritics: /[\u0074\u24E3\uFF54\u1E6B\u1E97\u0165\u1E6D\u021B\u0163\u1E71\u1E6F\u0167\u01AD\u0288\u2C66\uA787]/g
+  },
+  { letter: "th", diacritics: /[\u00FE]/g },
+  { letter: "tz", diacritics: /[\uA729]/g },
+  {
+    letter: "u",
+    diacritics: /[\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
+  },
+  {
+    letter: "v",
+    diacritics: /[\u0076\u24E5\uFF56\u1E7D\u1E7F\u028B\uA75F\u028C]/g
+  },
+  { letter: "vy", diacritics: /[\uA761]/g },
+  {
+    letter: "w",
+    diacritics: /[\u0077\u24E6\uFF57\u1E81\u1E83\u0175\u1E87\u1E85\u1E98\u1E89\u2C73]/g
+  },
+  { letter: "x", diacritics: /[\u0078\u24E7\uFF58\u1E8B\u1E8D]/g },
+  {
+    letter: "y",
+    diacritics: /[\u0079\u24E8\uFF59\u1EF3\u00FD\u0177\u1EF9\u0233\u1E8F\u00FF\u1EF7\u1E99\u1EF5\u01B4\u024F\u1EFF]/g
+  },
+  {
+    letter: "z",
+    diacritics: /[\u007A\u24E9\uFF5A\u017A\u1E91\u017C\u017E\u1E93\u1E95\u01B6\u0225\u0240\u2C6C\uA763]/g
+  }
+];
+// tslint:enable:max-line-length
+
+function nativeStringNormalize(s: string) {
+  /**
+   * NOTE: Normalizing accents/ diacritics in ES6.
+   * See https://bit.ly/2Cncgor for more info.
+   */
+  return s.normalize("NFD").replace(/[\u0300-\u036f]/g, "");
+}
+
+function stringNormalize(s: string) {
+  const normalized = diacritics.filter(n => n.diacritics.test(s));
+  return !normalized.length ? s : normalized[0].letter;
+}
+
+export function replaceDiacritics() {
+  return "function" === typeof "".normalize &&
+    "aeo" === nativeStringNormalize("áèö")
+    ? (s: string) => nativeStringNormalize(s)
+    : (s: string) => stringNormalize(s);
+}
diff --git a/index.ts b/index.ts
deleted file mode 100644
index 400b8f2..0000000
--- a/index.ts
+++ /dev/null
@@ -1,131 +0,0 @@
-export interface Diacritics {
-  letter: string;
-  diacritics: RegExp;
-}
-
-/**
- * NOTE: A more complete list of diacritics are from
- * {@link https://goo.gl/rEBH0E} and {@link https://goo.gl/9Niith}.
- */
-// tslint:disable:max-line-length
-export const diacritics: Diacritics[] = [
-  { letter: ' ', diacritics: /[\u00A0]/g },
-  { letter: '0', diacritics: /[\u07C0]/g },
-  { letter: 'A', diacritics: /[\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 },
-  { letter: 'AA', diacritics: /[\uA732]/g },
-  { letter: 'AE', diacritics: /[\u00C6\u01FC\u01E2]/g },
-  { letter: 'AO', diacritics: /[\uA734]/g },
-  { letter: 'AU', diacritics: /[\uA736]/g },
-  { letter: 'AV', diacritics: /[\uA738\uA73A]/g },
-  { letter: 'AY', diacritics: /[\uA73C]/g },
-  { letter: 'B', diacritics: /[\u0042\u24B7\uFF22\u1E02\u1E04\u1E06\u0243\u0182\u0181]/g },
-  { letter: 'C', diacritics: /[\u0043\u24B8\uFF23\u0106\u0108\u010A\u010C\u00C7\u1E08\u0187\u023B\uA73E]/g },
-  { letter: 'D', diacritics: /[\u0044\u24B9\uFF24\u1E0A\u010E\u1E0C\u1E10\u1E12\u1E0E\u0110\u018B\u018A\u0189\uA779]/g },
-  { letter: 'Dh', diacritics: /[\u00D0]/g },
-  { letter: 'DZ', diacritics: /[\u01F1\u01C4]/g },
-  { letter: 'Dz', diacritics: /[\u01F2\u01C5]/g },
-  { letter: 'E', diacritics: /[\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 },
-  { letter: 'F', diacritics: /[\u0046\u24BB\uFF26\u1E1E\u0191\uA77B]/g },
-  { letter: 'G', diacritics: /[\u0047\u24BC\uFF27\u01F4\u011C\u1E20\u011E\u0120\u01E6\u0122\u01E4\u0193\uA7A0\uA77D\uA77E]/g },
-  { letter: 'H', diacritics: /[\u0048\u24BD\uFF28\u0124\u1E22\u1E26\u021E\u1E24\u1E28\u1E2A\u0126\u2C67\u2C75\uA78D]/g },
-  { letter: 'I', diacritics: /[\u0049\u24BE\uFF29\u00CC\u00CD\u00CE\u0128\u012A\u012C\u0130\u00CF\u1E2E\u1EC8\u01CF\u0208\u020A\u1ECA\u012E\u1E2C\u0197]/g },
-  { letter: 'J', diacritics: /[\u004A\u24BF\uFF2A\u0134\u0248]/g },
-  { letter: 'K', diacritics: /[\u004B\u24C0\uFF2B\u1E30\u01E8\u1E32\u0136\u1E34\u0198\u2C69\uA740\uA742\uA744\uA7A2]/g },
-  { letter: 'L', diacritics: /[\u004C\u24C1\uFF2C\u013F\u0139\u013D\u1E36\u1E38\u013B\u1E3C\u1E3A\u0141\u023D\u2C62\u2C60\uA748\uA746\uA780]/g },
-  { letter: 'LJ', diacritics: /[\u01C7]/g },
-  { letter: 'Lj', diacritics: /[\u01C8]/g },
-  { letter: 'M', diacritics: /[\u004D\u24C2\uFF2D\u1E3E\u1E40\u1E42\u2C6E\u019C]/g },
-  { letter: 'N', diacritics: /[\u004E\u24C3\uFF2E\u01F8\u0143\u00D1\u1E44\u0147\u1E46\u0145\u1E4A\u1E48\u0220\u019D\uA790\uA7A4]/g },
-  { letter: 'NJ', diacritics: /[\u01CA]/g },
-  { letter: 'Nj', diacritics: /[\u01CB]/g },
-  { letter: 'O', diacritics: /[\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 },
-  { letter: 'OE', diacritics: /[\u0152]/g },
-  { letter: 'OI', diacritics: /[\u01A2]/g },
-  { letter: 'OO', diacritics: /[\uA74E]/g },
-  { letter: 'OU', diacritics: /[\u0222]/g },
-  { letter: 'P', diacritics: /[\u0050\u24C5\uFF30\u1E54\u1E56\u01A4\u2C63\uA750\uA752\uA754]/g },
-  { letter: 'Q', diacritics: /[\u0051\u24C6\uFF31\uA756\uA758\u024A]/g },
-  { letter: 'R', diacritics: /[\u0052\u24C7\uFF32\u0154\u1E58\u0158\u0210\u0212\u1E5A\u1E5C\u0156\u1E5E\u024C\u2C64\uA75A\uA7A6\uA782]/g },
-  { letter: 'S', diacritics: /[\u0053\u24C8\uFF33\u1E9E\u015A\u1E64\u015C\u1E60\u0160\u1E66\u1E62\u1E68\u0218\u015E\u2C7E\uA7A8\uA784]/g },
-  { letter: 'T', diacritics: /[\u0054\u24C9\uFF34\u1E6A\u0164\u1E6C\u021A\u0162\u1E70\u1E6E\u0166\u01AC\u01AE\u023E\uA786]/g },
-  { letter: 'Th', diacritics: /[\u00DE]/g },
-  { letter: 'TZ', diacritics: /[\uA728]/g },
-  { letter: 'U', diacritics: /[\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 },
-  { letter: 'V', diacritics: /[\u0056\u24CB\uFF36\u1E7C\u1E7E\u01B2\uA75E\u0245]/g },
-  { letter: 'VY', diacritics: /[\uA760]/g },
-  { letter: 'W', diacritics: /[\u0057\u24CC\uFF37\u1E80\u1E82\u0174\u1E86\u1E84\u1E88\u2C72]/g },
-  { letter: 'X', diacritics: /[\u0058\u24CD\uFF38\u1E8A\u1E8C]/g },
-  { letter: 'Y', diacritics: /[\u0059\u24CE\uFF39\u1EF2\u00DD\u0176\u1EF8\u0232\u1E8E\u0178\u1EF6\u1EF4\u01B3\u024E\u1EFE]/g },
-  { letter: 'Z', diacritics: /[\u005A\u24CF\uFF3A\u0179\u1E90\u017B\u017D\u1E92\u1E94\u01B5\u0224\u2C7F\u2C6B\uA762]/g },
-  { letter: 'a', diacritics: /[\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 },
-  { letter: 'aa', diacritics: /[\uA733]/g },
-  { letter: 'ae', diacritics: /[\u00E6\u01FD\u01E3]/g },
-  { letter: 'ao', diacritics: /[\uA735]/g },
-  { letter: 'au', diacritics: /[\uA737]/g },
-  { letter: 'av', diacritics: /[\uA739\uA73B]/g },
-  { letter: 'ay', diacritics: /[\uA73D]/g },
-  { letter: 'b', diacritics: /[\u0062\u24D1\uFF42\u1E03\u1E05\u1E07\u0180\u0183\u0253]/g },
-  { letter: 'c', diacritics: /[\u0063\u24D2\uFF43\u0107\u0109\u010B\u010D\u00E7\u1E09\u0188\u023C\uA73F\u2184]/g },
-  { letter: 'd', diacritics: /[\u0064\u24D3\uFF44\u1E0B\u010F\u1E0D\u1E11\u1E13\u1E0F\u0111\u018C\u0256\u0257\uA77A]/g },
-  { letter: 'dh', diacritics: /[\u00F0]/g },
-  { letter: 'dz', diacritics: /[\u01F3\u01C6]/g },
-  { letter: 'e', diacritics: /[\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 },
-  { letter: 'f', diacritics: /[\u0066\u24D5\uFF46\u1E1F\u0192\uA77C]/g },
-  { letter: 'ff', diacritics: /[\uFB00]/g },
-  { letter: 'fi', diacritics: /[\uFB01]/g },
-  { letter: 'fl', diacritics: /[\uFB02]/g },
-  { letter: 'ffi', diacritics: /[\uFB03]/g },
-  { letter: 'ffl', diacritics: /[\uFB04]/g },
-  { letter: 'g', diacritics: /[\u0067\u24D6\uFF47\u01F5\u011D\u1E21\u011F\u0121\u01E7\u0123\u01E5\u0260\uA7A1\u1D79\uA77F]/g },
-  { letter: 'h', diacritics: /[\u0068\u24D7\uFF48\u0125\u1E23\u1E27\u021F\u1E25\u1E29\u1E2B\u1E96\u0127\u2C68\u2C76\u0265]/g },
-  { letter: 'hv', diacritics: /[\u0195]/g },
-  { letter: 'i', diacritics: /[\u0069\u24D8\uFF49\u00EC\u00ED\u00EE\u0129\u012B\u012D\u00EF\u1E2F\u1EC9\u01D0\u0209\u020B\u1ECB\u012F\u1E2D\u0268\u0131]/g },
-  { letter: 'j', diacritics: /[\u006A\u24D9\uFF4A\u0135\u01F0\u0249]/g },
-  { letter: 'k', diacritics: /[\u006B\u24DA\uFF4B\u1E31\u01E9\u1E33\u0137\u1E35\u0199\u2C6A\uA741\uA743\uA745\uA7A3]/g },
-  { letter: 'l', diacritics: /[\u006C\u24DB\uFF4C\u0140\u013A\u013E\u1E37\u1E39\u013C\u1E3D\u1E3B\u017F\u0142\u019A\u026B\u2C61\uA749\uA781\uA747]/g },
-  { letter: 'lj', diacritics: /[\u01C9]/g },
-  { letter: 'm', diacritics: /[\u006D\u24DC\uFF4D\u1E3F\u1E41\u1E43\u0271\u026F]/g },
-  { letter: 'n', diacritics: /[\u006E\u24DD\uFF4E\u01F9\u0144\u00F1\u1E45\u0148\u1E47\u0146\u1E4B\u1E49\u019E\u0272\u0149\uA791\uA7A5]/g },
-  { letter: 'nj', diacritics: /[\u01CC]/g },
-  { letter: 'o', diacritics: /[\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 },
-  { letter: 'oe', diacritics: /[\u0153]/g },
-  { letter: 'oi', diacritics: /[\u01A3]/g },
-  { letter: 'ou', diacritics: /[\u0223]/g },
-  { letter: 'oo', diacritics: /[\uA74F]/g },
-  { letter: 'p', diacritics: /[\u0070\u24DF\uFF50\u1E55\u1E57\u01A5\u1D7D\uA751\uA753\uA755]/g },
-  { letter: 'q', diacritics: /[\u0071\u24E0\uFF51\u024B\uA757\uA759]/g },
-  { letter: 'r', diacritics: /[\u0072\u24E1\uFF52\u0155\u1E59\u0159\u0211\u0213\u1E5B\u1E5D\u0157\u1E5F\u024D\u027D\uA75B\uA7A7\uA783]/g },
-  { letter: 's', diacritics: /[\u0073\u24E2\uFF53\u00DF\u015B\u1E65\u015D\u1E61\u0161\u1E67\u1E63\u1E69\u0219\u015F\u023F\uA7A9\uA785\u1E9B]/g },
-  { letter: 'ss', diacritics: /[\xDF]/g },
-  { letter: 't', diacritics: /[\u0074\u24E3\uFF54\u1E6B\u1E97\u0165\u1E6D\u021B\u0163\u1E71\u1E6F\u0167\u01AD\u0288\u2C66\uA787]/g },
-  { letter: 'th', diacritics: /[\u00FE]/g },
-  { letter: 'tz', diacritics: /[\uA729]/g },
-  { letter: 'u', diacritics: /[\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 },
-  { letter: 'v', diacritics: /[\u0076\u24E5\uFF56\u1E7D\u1E7F\u028B\uA75F\u028C]/g },
-  { letter: 'vy', diacritics: /[\uA761]/g },
-  { letter: 'w', diacritics: /[\u0077\u24E6\uFF57\u1E81\u1E83\u0175\u1E87\u1E85\u1E98\u1E89\u2C73]/g },
-  { letter: 'x', diacritics: /[\u0078\u24E7\uFF58\u1E8B\u1E8D]/g },
-  { letter: 'y', diacritics: /[\u0079\u24E8\uFF59\u1EF3\u00FD\u0177\u1EF9\u0233\u1E8F\u00FF\u1EF7\u1E99\u1EF5\u01B4\u024F\u1EFF]/g },
-  { letter: 'z', diacritics: /[\u007A\u24E9\uFF5A\u017A\u1E91\u017C\u017E\u1E93\u1E95\u01B6\u0225\u0240\u2C6C\uA763]/g },
-];
-// tslint:enable:max-line-length
-
-function replaceDiacritics(inputChar: string) {
-  const normalized = diacritics.filter(n => n.diacritics.test(inputChar));
-
-  return Array.isArray(normalized) && normalized.length > 0 ? normalized[0].letter : inputChar;
-}
-
-export function normalizeSync(input?: string) {
-  if (typeof input !== 'string') {
-    throw new TypeError(`Expected 'input' to be of type string, but received '${input}'`);
-  }
-
-  return !input.length ? input : input.replace(/(\S)/g, (_, p: string) => replaceDiacritics(p));
-}
-
-export async function normalize(input?: string) {
-  return normalizeSync(input);
-}
-
-export default normalize;
diff --git a/mod.ts b/mod.ts
new file mode 100644
index 0000000..edc0299
--- /dev/null
+++ b/mod.ts
@@ -0,0 +1,22 @@
+import { replaceDiacritics } from "./helpers.ts";
+
+export function normalizeSync(input?: string | null): string | void {
+  if ("string" !== typeof input) {
+    throw new TypeError(
+      `Expected 'input' to be of type string, but received '${input}'`
+    );
+  }
+
+  const fn = replaceDiacritics();
+
+  return !input.length
+    ? input
+    : input.replace(/(\S)/g, (_, p: string) => fn(p));
+}
+
+export async function normalize(input?: string | null): Promise<string | void> {
+  return normalizeSync(input);
+}
+
+export { Diacritics, diacritics } from "./helpers.ts";
+export default normalize;
diff --git a/mod_test.mod.ts b/mod_test.mod.ts
new file mode 100644
index 0000000..0bfbf9c
--- /dev/null
+++ b/mod_test.mod.ts
@@ -0,0 +1,2 @@
+export * from "https://deno.land/std/testing/mod.ts";
+export * from "https://deno.land/std/testing/asserts.ts";
diff --git a/mod_test.ts b/mod_test.ts
new file mode 100644
index 0000000..d9162cf
--- /dev/null
+++ b/mod_test.ts
@@ -0,0 +1,110 @@
+import {
+  assertStrictEq,
+  assertEquals,
+  assertThrowsAsync,
+  runTests,
+  test
+} from "./mod_test.mod.ts";
+
+import { normalize } from "./mod.ts";
+import { replaceDiacritics } from "./helpers.ts";
+
+// void async function main() {
+//   const d = await normalize(null);
+//   console.log(d);
+// }();
+
+async function throwsWhenInvalidInput() {
+  await assertThrowsAsync(
+    async () => (normalize as (s: null) => Promise<void>)(null),
+    TypeError,
+    `Expected 'input' to be of type string, but received 'null'`
+  );
+}
+
+async function throwsWhenInputIsUndefined() {
+  await assertThrowsAsync(
+    async () => (normalize as (s?: string | null) => Promise<void>)(),
+    TypeError,
+    `Expected 'input' to be of type string, but received 'undefined'`
+  );
+}
+
+async function normalizesStrings() {
+  const strs = [
+    "Åland Islands",
+    "Saint Barthélemy",
+    "Cocos (Keeling) Islands",
+    "Côte d'Ivoire",
+    "Curaçao",
+    "Réunion"
+  ];
+
+  assertEquals(await Promise.all(strs.map(async n => normalize(n))), [
+    "Aland Islands",
+    "Saint Barthelemy",
+    "Cocos (Keeling) Islands",
+    "Cote d'Ivoire",
+    "Curacao",
+    "Reunion"
+  ]);
+}
+
+async function normalizesStringsWithoutUsingNativeFunction() {
+  const cachedFn = String.prototype.normalize;
+  String.prototype.normalize = null!;
+
+  try {
+    assertStrictEq(await normalize("Réunion"), "Reunion");
+  } catch (e) {
+    throw e;
+  } finally {
+    String.prototype.normalize = cachedFn;
+  }
+}
+
+async function returnsOriginalCharacterWhenNoMatchFound() {
+  const cachedFilter = Array.prototype.filter;
+  const cachedFn = String.prototype.normalize;
+  Array.prototype.filter = () => [];
+  String.prototype.normalize = null!;
+
+  try {
+    assertStrictEq(await normalize("Réunion"), "Réunion");
+  } catch (e) {
+    throw e;
+  } finally {
+    Array.prototype.filter = cachedFilter;
+    String.prototype.normalize = cachedFn;
+  }
+}
+
+async function normalizeSingleCharacter() {
+  assertStrictEq(await normalize("ô"), "o");
+}
+
+async function returnsEmptyStringUnTouched() {
+  assertStrictEq(await normalize(""), "");
+}
+
+async function useCorrectStringNormalizeFunction() {
+  const expected =
+    "function" === typeof "".normalize &&
+    "aeo" === "áèö".normalize("NFD").replace(/[\u0300-\u036f]/g, "")
+      ? "(s) => nativeStringNormalize(s)"
+      : "(s) => stringNormalize(s)";
+  assertStrictEq(replaceDiacritics().toString(), expected);
+}
+
+[
+  throwsWhenInvalidInput,
+  throwsWhenInputIsUndefined,
+  normalizesStrings,
+  normalizesStringsWithoutUsingNativeFunction,
+  returnsOriginalCharacterWhenNoMatchFound,
+  normalizeSingleCharacter,
+  returnsEmptyStringUnTouched,
+  useCorrectStringNormalizeFunction
+].map(n => test(n));
+
+runTests();
diff --git a/test/index.spec.ts b/test/index.spec.ts
deleted file mode 100644
index 8ffbbbe..0000000
--- a/test/index.spec.ts
+++ /dev/null
@@ -1,96 +0,0 @@
-import { test, assertEqual } from 'https://deno.land/x/testing/mod.ts';
-
-import { normalize } from '../index.ts';
-
-async function throwsWhenInvalidInput() {
-  try {
-    await normalize(null);
-  } catch (e) {
-    const err = new TypeError(`Expected 'input' to be of type string, but received 'null'`);
-    assertEqual(e, err);
-  }
-}
-
-async function throwsWhenInputIsUndefined() {
-  try {
-    await normalize();
-  } catch (e) {
-    const err = new TypeError(`Expected 'input' to be of type string, but received 'undefined'`);
-    assertEqual(e, err);
-  }
-}
-
-async function normalizesStrings() {
-  try {
-    const strs = [
-      'Åland Islands',
-      'Saint Barthélemy',
-      'Cocos (Keeling) Islands',
-      'Côte d\'Ivoire',
-      'Curaçao',
-      'Réunion',
-    ];
-
-    assertEqual(await normalize(strs[0]), 'Aland Islands');
-    assertEqual(await normalize(strs[1]), 'Saint Barthelemy');
-    assertEqual(await normalize(strs[2]), 'Cocos (Keeling) Islands');
-    assertEqual(await normalize(strs[3]), 'Cote d\'Ivoire');
-    assertEqual(await normalize(strs[4]), 'Curacao');
-    assertEqual(await normalize(strs[5]), 'Reunion');
-  } catch (e) {
-    throw e;
-  }
-}
-
-async function normalizesStringsWithoutUsingNativeFunction() {
-  const cachedFn = String.prototype.normalize;
-  String.prototype.normalize = null!;
-
-  try {
-    assertEqual(await normalize('Réunion'), 'Reunion');
-  } catch (e) {
-    throw e;
-  } finally {
-    String.prototype.normalize = cachedFn;
-  }
-}
-
-async function returnsOriginalCharacterWhenNoMatchFound() {
-  const cachedFilter = Array.prototype.filter;
-  const cachedFn = String.prototype.normalize;
-  Array.prototype.filter = () => [];
-  String.prototype.normalize = null!;
-
-  try {
-    assertEqual(await normalize('Réunion'), 'Réunion');
-  } catch (e) {
-    throw e;
-  } finally {
-    Array.prototype.filter = cachedFilter;
-    String.prototype.normalize = cachedFn;
-  }
-}
-
-async function normalizeSingleCharacter() {
-  assertEqual(await normalize('ô'), 'o');
-}
-
-async function returnsEmptyStringUnTouched() {
-  assertEqual(await normalize(''), '');
-}
-
-Promise.all([
-  throwsWhenInvalidInput,
-  throwsWhenInputIsUndefined,
-  normalizesStringsWithoutUsingNativeFunction,
-  returnsOriginalCharacterWhenNoMatchFound,
-  normalizeSingleCharacter,
-  returnsEmptyStringUnTouched,
-].map(n => test(n)));
-
-/**
- * FIXME: String#normalize is not working on `deno`.
- *
- * Related issue: https://github.com/denoland/deno/issues/627
- */
-test(normalizesStrings);