diff --git a/.npmignore b/.npmignore
new file mode 100644
index 0000000..3e00276
--- /dev/null
+++ b/.npmignore
@@ -0,0 +1,2 @@
+tsconfig.json
+src
\ No newline at end of file
diff --git a/dist/config.d.ts b/dist/config.d.ts
new file mode 100644
index 0000000..af2b8ec
--- /dev/null
+++ b/dist/config.d.ts
@@ -0,0 +1,28 @@
+interface Formats {
+    number: Record<string, any>;
+    date: Record<string, any>;
+    time: Record<string, any>;
+}
+interface Options {
+    fallbackLocale: string;
+    initialLocale: string;
+    formats: Formats;
+    loadingDelay: number;
+    warnOnMissingMessages: boolean;
+}
+interface GetClientLocaleOptions {
+    navigator?: boolean;
+    hash?: string;
+    search?: string;
+    pathname?: RegExp;
+    hostname?: RegExp;
+}
+interface ConfigureOptions {
+    fallbackLocale: string;
+    initialLocale?: string | GetClientLocaleOptions;
+    formats?: Partial<Formats>;
+    loadingDelay?: number;
+}
+export declare function init(opts: ConfigureOptions): void;
+export declare function getOptions(): Options;
+export {};
diff --git a/dist/config.js b/dist/config.js
new file mode 100644
index 0000000..36e6dcf
--- /dev/null
+++ b/dist/config.js
@@ -0,0 +1,111 @@
+import { currentLocale } from "./stores";
+const defaultFormats = {
+    number: {
+        scientific: { notation: "scientific" },
+        engineering: { notation: "engineering" },
+        compactLong: { notation: "compact", compactDisplay: "long" },
+        compactShort: { notation: "compact", compactDisplay: "short" }
+    },
+    date: {
+        short: { month: "numeric", day: "numeric", year: "2-digit" },
+        medium: { month: "short", day: "numeric", year: "numeric" },
+        long: { month: "long", day: "numeric", year: "numeric" },
+        full: { weekday: "long", month: "long", day: "numeric", year: "numeric" }
+    },
+    time: {
+        short: { hour: "numeric", minute: "numeric" },
+        medium: { hour: "numeric", minute: "numeric", second: "numeric" },
+        long: {
+            hour: "numeric",
+            minute: "numeric",
+            second: "numeric",
+            timeZoneName: "short"
+        },
+        full: {
+            hour: "numeric",
+            minute: "numeric",
+            second: "numeric",
+            timeZoneName: "short"
+        }
+    }
+};
+const defaultOptions = {
+    fallbackLocale: null,
+    initialLocale: null,
+    loadingDelay: 200,
+    formats: defaultFormats,
+    warnOnMissingMessages: true
+};
+const options = defaultOptions;
+const getFromQueryString = (queryString, key) => {
+    const keyVal = queryString.split("&").find(i => i.indexOf(`${key}=`) === 0);
+    if (keyVal) {
+        return keyVal.split("=").pop();
+    }
+    return null;
+};
+const getFirstMatch = (base, pattern) => {
+    const match = pattern.exec(base);
+    // istanbul ignore if
+    if (!match)
+        return null;
+    // istanbul ignore else
+    return match[1] || null;
+};
+function getClientLocale({ navigator, hash, search, pathname, hostname }) {
+    let locale;
+    // istanbul ignore next
+    if (typeof window === "undefined")
+        return null;
+    if (hostname) {
+        locale = getFirstMatch(window.location.hostname, hostname);
+        if (locale)
+            return locale;
+    }
+    if (pathname) {
+        locale = getFirstMatch(window.location.pathname, pathname);
+        if (locale)
+            return locale;
+    }
+    if (navigator) {
+        // istanbul ignore else
+        locale = window.navigator.language || window.navigator.languages[0];
+        if (locale)
+            return locale;
+    }
+    if (search) {
+        locale = getFromQueryString(window.location.search.substr(1), search);
+        if (locale)
+            return locale;
+    }
+    if (hash) {
+        locale = getFromQueryString(window.location.hash.substr(1), hash);
+        if (locale)
+            return locale;
+    }
+    return null;
+}
+export function init(opts) {
+    const { formats, ...rest } = opts;
+    const initialLocale = opts.initialLocale
+        ? typeof opts.initialLocale === "string"
+            ? opts.initialLocale
+            : getClientLocale(opts.initialLocale) || opts.fallbackLocale
+        : opts.fallbackLocale;
+    Object.assign(options, rest, { initialLocale });
+    if (formats) {
+        if ("number" in formats) {
+            Object.assign(options.formats.number, formats.number);
+        }
+        if ("date" in formats) {
+            Object.assign(options.formats.date, formats.date);
+        }
+        if ("time" in formats) {
+            Object.assign(options.formats.time, formats.time);
+        }
+    }
+    return currentLocale.set(initialLocale);
+}
+export function getOptions() {
+    return options;
+}
diff --git a/dist/formatters.d.ts b/dist/formatters.d.ts
new file mode 100644
index 0000000..6f038a8
--- /dev/null
+++ b/dist/formatters.d.ts
@@ -0,0 +1,14 @@
+declare type IntlFormatterOptions<T> = T & {
+    format?: string;
+    locale?: string;
+};
+interface MemoizedIntlFormatter<T, U> {
+    (options?: IntlFormatterOptions<U>): T;
+}
+export declare const getNumberFormatter: MemoizedIntlFormatter<Intl.NumberFormat, Intl.NumberFormatOptions>;
+export declare const getDateFormatter: MemoizedIntlFormatter<Intl.DateTimeFormat, Intl.DateTimeFormatOptions>;
+export declare const getTimeFormatter: MemoizedIntlFormatter<Intl.DateTimeFormat, Intl.DateTimeFormatOptions>;
+export declare const formatTime: (t: Date, options: Record<string, any>) => string;
+export declare const formatDate: (d: Date, options: Record<string, any>) => string;
+export declare const formatNumber: (n: number, options: Record<string, any>) => string;
+export {};
diff --git a/dist/formatters.js b/dist/formatters.js
new file mode 100644
index 0000000..36c3757
--- /dev/null
+++ b/dist/formatters.js
@@ -0,0 +1,124 @@
+import { getCurrentLocale } from './stores';
+import { getOptions } from './config';
+import { monadicMemoize } from './memoize';
+const getIntlFormatterOptions = (type, name) => {
+    const formats = getOptions().formats;
+    if (type in formats && name in formats[type]) {
+        return formats[type][name];
+    }
+    throw new Error(`[icu-helpers] Unknown "${name}" ${type} format.`);
+};
+export const getNumberFormatter = monadicMemoize(({ locale, format, ...options } = {}) => {
+    locale = locale || getCurrentLocale();
+    if (locale == null) {
+        throw new Error('[icu-helpers] A "locale" must be set to format numbers');
+    }
+    if (format) {
+        options = getIntlFormatterOptions('number', format);
+    }
+    return new Intl.NumberFormat(locale, options);
+});
+export const getDateFormatter = monadicMemoize(({ locale, format, ...options } = {}) => {
+    locale = locale || getCurrentLocale();
+    if (locale == null) {
+        throw new Error('[icu-helpers] A "locale" must be set to format dates');
+    }
+    if (format)
+        options = getIntlFormatterOptions('date', format);
+    else if (Object.keys(options).length === 0) {
+        options = getIntlFormatterOptions('date', 'short');
+    }
+    return new Intl.DateTimeFormat(locale, options);
+});
+export const getTimeFormatter = monadicMemoize(({ locale, format, ...options } = {}) => {
+    locale = locale || getCurrentLocale();
+    if (locale == null) {
+        throw new Error('[svelte-i18n] A "locale" must be set to format time values');
+    }
+    if (format)
+        options = getIntlFormatterOptions('time', format);
+    else if (Object.keys(options).length === 0) {
+        options = getIntlFormatterOptions('time', 'short');
+    }
+    return new Intl.DateTimeFormat(locale, options);
+});
+export const formatTime = (t, options) => getTimeFormatter(options).format(t);
+export const formatDate = (d, options) => getDateFormatter(options).format(d);
+export const formatNumber = (n, options) => getNumberFormatter(options).format(n);
+// import { getOptions } from "./config";
+// const CACHED = Object.create(null);
+// export function formatterOptions(type, style) {
+//   return getOptions().formats[type][style] || {};
+// }
+// const getIntlFormatterOptions = (type, name) => {
+//   const formats = getOptions().formats
+//   if (type in formats && name in formats[type]) {
+//     return formats[type][name]
+//   }
+//   throw new Error(`[icu-helpers] Unknown "${name}" ${type} format.`)
+// }
+// // const getIntlFormatterOptions = (
+// //   type: 'time' | 'number' | 'date',
+// //   name: string
+// // ): any => {
+// //   const formats = getOptions().formats
+// //   if (type in formats && name in formats[type]) {
+// //     return formats[type][name]
+// //   }
+// //   throw new Error(`[svelte-i18n] Unknown "${name}" ${type} format.`)
+// // }
+// // export const getNumberFormatter: MemoizedIntlFormatter<
+// //   Intl.NumberFormat,
+// //   Intl.NumberFormatOptions
+// // > = monadicMemoize(({ locale, format, ...options } = {}) => {
+// //   locale = locale || getCurrentLocale()
+// //   if (locale == null) {
+// //     throw new Error('[svelte-i18n] A "locale" must be set to format numbers')
+// //   }
+// //   if (format) {
+// //     options = getIntlFormatterOptions('number', format)
+// //   }
+// //   return new Intl.NumberFormat(locale, options)
+// // })
+// // export const getDateFormatter: MemoizedIntlFormatter<
+// //   Intl.DateTimeFormat,
+// //   Intl.DateTimeFormatOptions
+// // > = monadicMemoize(({ locale, format, ...options } = {}) => {
+// //   locale = locale || getCurrentLocale()
+// //   if (locale == null) {
+// //     throw new Error('[svelte-i18n] A "locale" must be set to format dates')
+// //   }
+// //   if (format) options = getIntlFormatterOptions('date', format)
+// //   else if (Object.keys(options).length === 0) {
+// //     options = getIntlFormatterOptions('date', 'short')
+// //   }
+// //   return new Intl.DateTimeFormat(locale, options)
+// // })
+// // export const getTimeFormatter: MemoizedIntlFormatter<
+// //   Intl.DateTimeFormat,
+// //   Intl.DateTimeFormatOptions
+// // > = monadicMemoize(({ locale, format, ...options } = {}) => {
+// //   locale = locale || getCurrentLocale()
+// //   if (locale == null) {
+// //     throw new Error(
+// //       '[svelte-i18n] A "locale" must be set to format time values'
+// //     )
+// //   }
+// //   if (format) options = getIntlFormatterOptions('time', format)
+// //   else if (Object.keys(options).length === 0) {
+// //     options = getIntlFormatterOptions('time', 'short')
+// //   }
+// //   return new Intl.DateTimeFormat(locale, options)
+// // })
+// // export function getNumberFormatter({ locale, format, ...options }) {
+// //   let key = "number" + locale + JSON.stringify(opts);
+// //   return CACHED[key] || (CACHED[key] = new Intl.NumberFormat(locale, opts));
+// // }
+// // export function getDateFormatter(locale, opts) {
+// //   let key = "date" + locale + JSON.stringify(opts);
+// //   return CACHED[key] || (CACHED[key] = new Intl.DateTimeFormat(locale, opts));
+// // }
+// // export function getTimeFormatter(locale, opts) {
+// //   let key = "time" + locale + JSON.stringify(opts);
+// //   return CACHED[key] || (CACHED[key] = new Intl.DateTimeFormat(locale, opts));
+// // }
diff --git a/dist/index.d.ts b/dist/index.d.ts
new file mode 100644
index 0000000..0bdd288
--- /dev/null
+++ b/dist/index.d.ts
@@ -0,0 +1,14 @@
+import { init } from "./config";
+import { currentLocale, dictionary, locales, LocaleDictionary } from "./stores";
+import { getNumberFormatter, getDateFormatter, getTimeFormatter, formatTime, formatDate, formatNumber } from "./formatters";
+declare type PluralRule = "zero" | "one" | "two" | "few" | "many" | "other" | number;
+declare type PluralOptions = Record<PluralRule, string>;
+export declare function __interpolate(value: any): any;
+export declare function __plural(value: number, offsetOrOptions: number | PluralOptions, opts?: PluralOptions): string;
+export declare function __select(value: any, opts: Record<any, string>): string;
+export declare function __number(value: number, format?: string): string;
+export declare function __date(value: Date, format?: string): string;
+export declare function __time(value: Date, format?: string): string;
+export declare function addMessages(locale: string, messages: LocaleDictionary): void;
+export declare function lookupMessage(key: string, locale?: string): string;
+export { init, currentLocale, dictionary, locales, getNumberFormatter, getDateFormatter, getTimeFormatter, formatTime, formatDate, formatNumber };
diff --git a/dist/index.js b/dist/index.js
new file mode 100644
index 0000000..d74cb1c
--- /dev/null
+++ b/dist/index.js
@@ -0,0 +1,46 @@
+import { init } from "./config";
+import { currentLocale, dictionary, locales, getCurrentLocale } from "./stores";
+import { getNumberFormatter, getDateFormatter, getTimeFormatter, formatTime, formatDate, formatNumber } from "./formatters";
+export function __interpolate(value) {
+    return value === 0 ? 0 : value || '';
+}
+const PLURAL_RULES = Object.create(null);
+function getLocalPluralFor(v) {
+    let loc = getCurrentLocale();
+    let pluralRules = PLURAL_RULES[loc] || (PLURAL_RULES[loc] = new Intl.PluralRules(loc));
+    return pluralRules.select(v);
+}
+export function __plural(value, offsetOrOptions, opts) {
+    if (typeof offsetOrOptions === "number") {
+        return (opts[value] ||
+            opts[getLocalPluralFor(value - offsetOrOptions)] ||
+            "");
+    }
+    else {
+        return (offsetOrOptions[value] ||
+            offsetOrOptions[getLocalPluralFor(value)] ||
+            "");
+    }
+}
+export function __select(value, opts) {
+    return opts[value] || opts['other'] || '';
+}
+export function __number(value, format) {
+    return formatNumber(value, { format });
+}
+export function __date(value, format = "short") {
+    return formatDate(value, { format });
+}
+export function __time(value, format = "short") {
+    return formatTime(value, { format });
+}
+export function addMessages(locale, messages) {
+    dictionary.update(value => {
+        value[locale] = Object.assign(value[locale] || {}, messages);
+        return value;
+    });
+}
+export function lookupMessage(key, locale = getCurrentLocale()) {
+    return dictionary._value[locale][key];
+}
+export { init, currentLocale, dictionary, locales, getNumberFormatter, getDateFormatter, getTimeFormatter, formatTime, formatDate, formatNumber };
diff --git a/dist/memoize.d.ts b/dist/memoize.d.ts
new file mode 100644
index 0000000..dc035a2
--- /dev/null
+++ b/dist/memoize.d.ts
@@ -0,0 +1,3 @@
+declare type MemoizedFunction = <F extends any>(fn: F) => F;
+declare const monadicMemoize: MemoizedFunction;
+export { monadicMemoize };
diff --git a/dist/memoize.js b/dist/memoize.js
new file mode 100644
index 0000000..116b340
--- /dev/null
+++ b/dist/memoize.js
@@ -0,0 +1,12 @@
+const monadicMemoize = fn => {
+    const cache = Object.create(null);
+    const memoizedFn = (arg) => {
+        const cacheKey = JSON.stringify(arg);
+        if (cacheKey in cache) {
+            return cache[cacheKey];
+        }
+        return (cache[cacheKey] = fn(arg));
+    };
+    return memoizedFn;
+};
+export { monadicMemoize };
diff --git a/dist/stores.d.ts b/dist/stores.d.ts
new file mode 100644
index 0000000..dafd1bf
--- /dev/null
+++ b/dist/stores.d.ts
@@ -0,0 +1,14 @@
+declare class WritableStore<T> {
+    _value: T;
+    _subscribers: ((T: any) => void)[];
+    constructor(v: any);
+    subscribe(fn: (value: T) => void): () => ((T: any) => void)[];
+    set(v: T): void;
+    update(cb: (value: T) => T): void;
+}
+export declare type LocaleDictionary = Record<string, string>;
+export declare const currentLocale: WritableStore<string>;
+export declare const dictionary: WritableStore<Record<string, Record<string, string>>>;
+export declare const locales: WritableStore<string[]>;
+export declare function getCurrentLocale(): string;
+export {};
diff --git a/dist/stores.js b/dist/stores.js
new file mode 100644
index 0000000..9edcac9
--- /dev/null
+++ b/dist/stores.js
@@ -0,0 +1,29 @@
+// This was a svelte-only library, it could be a writable store
+class WritableStore {
+    constructor(v) {
+        this._value = v;
+        this._subscribers = [];
+    }
+    subscribe(fn) {
+        this._subscribers.push(fn);
+        fn(this._value);
+        return () => this._subscribers.splice(this._subscribers.indexOf(fn), 1);
+    }
+    set(v) {
+        this._value = v;
+        this._subscribers.forEach(fn => fn(v));
+    }
+    update(cb) {
+        this._value = cb(this._value);
+        this._subscribers.forEach(fn => fn(this._value));
+    }
+}
+export const currentLocale = new WritableStore(undefined);
+export const dictionary = new WritableStore({});
+export const locales = new WritableStore([]);
+dictionary.subscribe(dict => {
+    locales.set(Object.keys(dict));
+});
+export function getCurrentLocale() {
+    return currentLocale._value;
+}
diff --git a/package-lock.json b/package-lock.json
index 79e1a8b..206b290 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1092,6 +1092,25 @@
         "@types/yargs": "^13.0.0"
       }
     },
+    "@rollup/plugin-typescript": {
+      "version": "2.1.0",
+      "resolved": "https://registry.npmjs.org/@rollup/plugin-typescript/-/plugin-typescript-2.1.0.tgz",
+      "integrity": "sha512-7lXKGY06aofrceVez/YnN2axttFdHSqlUBpCJ6ebzDfxwLDKMgSV5lD4ykBcdgE7aK3egxuLkD/HKyRB5L8Log==",
+      "dev": true,
+      "requires": {
+        "@rollup/pluginutils": "^3.0.0",
+        "resolve": "^1.13.1"
+      }
+    },
+    "@rollup/pluginutils": {
+      "version": "3.0.4",
+      "resolved": "https://registry.npmjs.org/@rollup/pluginutils/-/pluginutils-3.0.4.tgz",
+      "integrity": "sha512-buc0oeq2zqQu2mpMyvZgAaQvitikYjT/4JYhA4EXwxX8/g0ZGHoGiX+0AwmfhrNqH4oJv67gn80sTZFQ/jL1bw==",
+      "dev": true,
+      "requires": {
+        "estree-walker": "^0.6.1"
+      }
+    },
     "@types/babel__core": {
       "version": "7.1.3",
       "resolved": "https://registry.npmjs.org/@types/babel__core/-/babel__core-7.1.3.tgz",
@@ -2026,6 +2045,12 @@
       "integrity": "sha512-39nnKffWz8xN1BU/2c79n9nB9HDzo0niYUqx6xyqUnyoAnQyyWpOTdZEeiCch8BBu515t4wp9ZmgVfVhn9EBpw==",
       "dev": true
     },
+    "estree-walker": {
+      "version": "0.6.1",
+      "resolved": "https://registry.npmjs.org/estree-walker/-/estree-walker-0.6.1.tgz",
+      "integrity": "sha512-SqmZANLWS0mnatqbSfRP5g8OXZC12Fgg1IwNtLsyHDzJizORW4khDfjPqJZsemPWBB2uqykUah5YpQ6epsqC/w==",
+      "dev": true
+    },
     "esutils": {
       "version": "2.0.3",
       "resolved": "https://registry.npmjs.org/esutils/-/esutils-2.0.3.tgz",
@@ -5392,6 +5417,12 @@
         "prelude-ls": "~1.1.2"
       }
     },
+    "typescript": {
+      "version": "3.7.5",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-3.7.5.tgz",
+      "integrity": "sha512-/P5lkRXkWHNAbcJIiHPfRoKqyd7bsyCma1hZNUGfn20qm64T6ZBlrzprymeu918H+mB/0rIg2gGK/BXkhhYgBw==",
+      "dev": true
+    },
     "unicode-canonical-property-names-ecmascript": {
       "version": "1.0.4",
       "resolved": "https://registry.npmjs.org/unicode-canonical-property-names-ecmascript/-/unicode-canonical-property-names-ecmascript-1.0.4.tgz",
diff --git a/package.json b/package.json
index 606f1ca..790ed5b 100644
--- a/package.json
+++ b/package.json
@@ -5,13 +5,11 @@
   "repository": "",
   "license": "MIT",
   "scripts": {
+    "build": "tsc",
     "test": "jest test"
   },
-  "publishConfig": {
-    "access": "public"
-  },
-  "main": "src/index.js",
-  "module": "src/index.js",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
   "dependencies": {},
   "keywords": [
     "babel-plugin",
@@ -19,6 +17,8 @@
   ],
   "devDependencies": {
     "@babel/preset-env": "^7.0.0",
+    "@rollup/plugin-typescript": "^2.1.0",
+    "typescript": "^3.7.5",
     "babel-jest": "^24.9.0",
     "jest": "^24.9.0"
   }
diff --git a/src/config.js b/src/config.ts
similarity index 76%
rename from src/config.js
rename to src/config.ts
index 9214e9e..3e8d6f2 100644
--- a/src/config.js
+++ b/src/config.ts
@@ -1,6 +1,34 @@
 import { currentLocale } from "./stores";
+interface Formats {
+  number: Record<string, any>
+  date: Record<string, any>
+  time: Record<string, any>
+}
+
+interface Options {
+  fallbackLocale: string
+  initialLocale: string
+  formats: Formats
+  loadingDelay: number
+  warnOnMissingMessages: boolean
+}
+
+interface GetClientLocaleOptions {
+  navigator?: boolean;
+  hash?: string;
+  search?: string;
+  pathname?: RegExp;
+  hostname?: RegExp;
+}
+
+interface ConfigureOptions {
+  fallbackLocale: string;
+  initialLocale?: string | GetClientLocaleOptions;
+  formats?: Partial<Formats>;
+  loadingDelay?: number;
+}
 
-const defaultFormats = {
+const defaultFormats: Formats = {
   number: {
     scientific: { notation: "scientific" },
     engineering: { notation: "engineering" },
@@ -31,14 +59,15 @@ const defaultFormats = {
   }
 };
 
-const defaultOptions = {
+const defaultOptions: Options = {
   fallbackLocale: null,
   initialLocale: null,
   loadingDelay: 200,
   formats: defaultFormats,
   warnOnMissingMessages: true
 };
-const options = defaultOptions;
+const options: Options = defaultOptions;
+
 const getFromQueryString = (queryString, key) => {
   const keyVal = queryString.split("&").find(i => i.indexOf(`${key}=`) === 0);
 
@@ -56,7 +85,13 @@ const getFirstMatch = (base, pattern) => {
   return match[1] || null;
 };
 
-function getClientLocale({ navigator, hash, search, pathname, hostname }) {
+function getClientLocale({
+  navigator,
+  hash,
+  search,
+  pathname,
+  hostname
+}: GetClientLocaleOptions) {
   let locale;
 
   // istanbul ignore next
@@ -91,7 +126,7 @@ function getClientLocale({ navigator, hash, search, pathname, hostname }) {
   return null;
 }
 
-export function init(opts) {
+export function init(opts: ConfigureOptions) {
   const { formats, ...rest } = opts;
   const initialLocale = opts.initialLocale
     ? typeof opts.initialLocale === "string"
@@ -116,6 +151,6 @@ export function init(opts) {
   return currentLocale.set(initialLocale);
 }
 
-export function getOptions() {
+export function getOptions(): Options {
   return options;
 }
\ No newline at end of file
diff --git a/src/formatters.js b/src/formatters.ts
similarity index 82%
rename from src/formatters.js
rename to src/formatters.ts
index 88b195f..aef2420 100644
--- a/src/formatters.js
+++ b/src/formatters.ts
@@ -2,6 +2,15 @@ import { getCurrentLocale } from './stores'
 import { getOptions } from './config'
 import { monadicMemoize } from './memoize'
 
+type IntlFormatterOptions<T> = T & {
+  format?: string
+  locale?: string
+}
+
+interface MemoizedIntlFormatter<T, U> {
+  (options?: IntlFormatterOptions<U>): T;
+}
+
 const getIntlFormatterOptions = (type, name) => {
   const formats = getOptions().formats
   if (type in formats && name in formats[type]) {
@@ -11,7 +20,10 @@ const getIntlFormatterOptions = (type, name) => {
   throw new Error(`[icu-helpers] Unknown "${name}" ${type} format.`)
 }
 
-export const getNumberFormatter = monadicMemoize(({ locale, format, ...options } = {}) => {
+export const getNumberFormatter: MemoizedIntlFormatter<
+  Intl.NumberFormat,
+  Intl.NumberFormatOptions
+> = monadicMemoize(({ locale, format, ...options } = {}) => {
   locale = locale || getCurrentLocale()
   if (locale == null) {
     throw new Error('[icu-helpers] A "locale" must be set to format numbers')
@@ -24,7 +36,10 @@ export const getNumberFormatter = monadicMemoize(({ locale, format, ...options }
   return new Intl.NumberFormat(locale, options)
 })
 
-export const getDateFormatter = monadicMemoize(({ locale, format, ...options } = {}) => {
+export const getDateFormatter: MemoizedIntlFormatter<
+  Intl.DateTimeFormat,
+  Intl.DateTimeFormatOptions
+> = monadicMemoize(({ locale, format, ...options } = {}) => {
   locale = locale || getCurrentLocale()
   if (locale == null) {
     throw new Error('[icu-helpers] A "locale" must be set to format dates')
@@ -38,7 +53,10 @@ export const getDateFormatter = monadicMemoize(({ locale, format, ...options } =
   return new Intl.DateTimeFormat(locale, options)
 })
 
-export const getTimeFormatter = monadicMemoize(({ locale, format, ...options } = {}) => {
+export const getTimeFormatter: MemoizedIntlFormatter<
+  Intl.DateTimeFormat,
+  Intl.DateTimeFormatOptions
+> = monadicMemoize(({ locale, format, ...options } = {}) => {
   locale = locale || getCurrentLocale()
   if (locale == null) {
     throw new Error(
@@ -54,9 +72,12 @@ export const getTimeFormatter = monadicMemoize(({ locale, format, ...options } =
   return new Intl.DateTimeFormat(locale, options)
 })
 
-export const formatTime = (t, options) => getTimeFormatter(options).format(t);
-export const formatDate = (d, options) => getDateFormatter(options).format(d);
-export const formatNumber = (n, options) => getNumberFormatter(options).format(n);
+export const formatTime = (t: Date, options: Record<string, any>) =>
+  getTimeFormatter(options).format(t);
+export const formatDate = (d: Date, options: Record<string, any>) =>
+  getDateFormatter(options).format(d);
+export const formatNumber = (n: number, options: Record<string, any>) =>
+  getNumberFormatter(options).format(n);
 
 // import { getOptions } from "./config";
 
diff --git a/src/index.d.ts b/src/index.d.ts
deleted file mode 100644
index 2d17441..0000000
--- a/src/index.d.ts
+++ /dev/null
@@ -1,22 +0,0 @@
-declare module "icu-helpers" {
-  type MessageFn = (...args: any) => string
-  interface WritableStore {
-    subscribe: (v: any) => () => {}
-    set(v: any): void
-    update(cb: () => {}): void
-    clear(): void
-  }
-  export const currentLocale: WritableStore
-  export const locales: WritableStore
-  export const dictionary: WritableStore
-  declare function addMessages(locale: any, messages: any): void
-  declare function setLocale(locale: string): void
-  declare function lookupMessage(key: string, locale?: string): string | MessageFn
-  declare function init(Record): void
-  declare function getDateFormatter(opts: any): Intl.NumberFormat
-  declare function getNumberFormatter(opts: any): Intl.DateTimeFormat
-  declare function getTimeFormatter(opts: any): Intl.DateTimeFormat
-  declare function formatTime(value: Date): string
-  declare function formatDate(value: Date): string
-  declare function formatNumber(value: Number): string
-}
\ No newline at end of file
diff --git a/src/index.js b/src/index.js
deleted file mode 100644
index a227979..0000000
--- a/src/index.js
+++ /dev/null
@@ -1,69 +0,0 @@
-
-import { init } from "./config";
-import { currentLocale, dictionary, locales } from './stores';
-import {
-  // formatterOptions,
-  getNumberFormatter,
-  getDateFormatter,
-  getTimeFormatter,
-  formatTime,
-  formatDate,
-  formatNumber
-} from "./formatters";
-
-export function __interpolate(value) {
-  return value === 0 ? 0 : value || '';
-}
-
-const PLURAL_RULES = Object.create(null);
-function getLocalPluralFor(v) {
-  let pluralRules = PLURAL_RULES[currentLocale._value] || (PLURAL_RULES[currentLocale._value] = new Intl.PluralRules(currentLocale._value));
-  return pluralRules.select(v);
-}
-export function __plural(value, offsetOrOptions, opts) {
-  if (typeof offsetOrOptions === 'number') {
-    return opts[value] || opts[getLocalPluralFor(value - offsetOrOptions)] || "";
-  } else {
-    return offsetOrOptions[value] || offsetOrOptions[getLocalPluralFor(value)] || "";
-  }
-}
-
-export function __select(value, opts) {
-  return opts[value] || opts['other'];
-}
-
-export function __number(value, format) {
-  return formatNumber(value, { format });
-}
-
-export function __date(value, format = "short") {
-  return formatDate(value, { format });
-}
-
-export function __time(value, format = "short") {
-  return formatTime(value, { format });
-}
-
-export function addMessages(locale, messages) {
-  dictionary.update(value => {
-    value[locale] = Object.assign(value[locale] || {}, messages);
-    return value;
-  });
-}
-
-export function lookupMessage(key, locale = currentLocale._value) {
-  return dictionary._value[locale][key];
-}
-
-export {
-  init,
-  currentLocale,
-  dictionary,
-  locales,
-  getNumberFormatter,
-  getDateFormatter,
-  getTimeFormatter,
-  formatTime,
-  formatDate,
-  formatNumber
-};
\ No newline at end of file
diff --git a/src/index.ts b/src/index.ts
new file mode 100644
index 0000000..3fa9571
--- /dev/null
+++ b/src/index.ts
@@ -0,0 +1,89 @@
+
+import { init } from "./config";
+import {
+  currentLocale,
+  dictionary,
+  locales,
+  getCurrentLocale,
+  LocaleDictionary
+} from "./stores";
+import {
+  getNumberFormatter,
+  getDateFormatter,
+  getTimeFormatter,
+  formatTime,
+  formatDate,
+  formatNumber
+} from "./formatters";
+
+type PluralRule = "zero" | "one" | "two" | "few" | "many" | "other" | number
+type PluralOptions = Record<PluralRule, string>
+export function __interpolate(value: any) {
+  return value === 0 ? 0 : value || '';
+}
+
+const PLURAL_RULES = Object.create(null);
+function getLocalPluralFor(v: number): PluralRule {
+  let loc = getCurrentLocale();
+  let pluralRules = PLURAL_RULES[loc] || (PLURAL_RULES[loc] = new Intl.PluralRules(loc));
+  return pluralRules.select(v);
+}
+export function __plural(
+  value: number,
+  offsetOrOptions: number | PluralOptions,
+  opts?: PluralOptions
+): string {
+  if (typeof offsetOrOptions === "number") {
+    return (
+      opts[value] ||
+      opts[getLocalPluralFor(value - offsetOrOptions)] ||
+      ""
+    );
+  } else {
+    return (
+      offsetOrOptions[value] ||
+      offsetOrOptions[getLocalPluralFor(value)] ||
+      ""
+    );
+  }
+}
+
+export function __select(value: any, opts: Record<any, string>): string {
+  return opts[value] || opts['other'] || '';
+}
+
+export function __number(value: number, format?: string): string {
+  return formatNumber(value, { format });
+}
+
+export function __date(value: Date, format = "short"): string {
+  return formatDate(value, { format });
+}
+
+export function __time(value: Date, format = "short"): string {
+  return formatTime(value, { format });
+}
+
+export function addMessages(locale: string, messages: LocaleDictionary): void {
+  dictionary.update(value => {
+    value[locale] = Object.assign(value[locale] || {}, messages);
+    return value;
+  });
+}
+
+export function lookupMessage(key: string, locale: string = getCurrentLocale()) {
+  return dictionary._value[locale][key];
+}
+
+export {
+  init,
+  currentLocale,
+  dictionary,
+  locales,
+  getNumberFormatter,
+  getDateFormatter,
+  getTimeFormatter,
+  formatTime,
+  formatDate,
+  formatNumber
+};
\ No newline at end of file
diff --git a/src/memoize.js b/src/memoize.js
deleted file mode 100644
index 7d2f0dd..0000000
--- a/src/memoize.js
+++ /dev/null
@@ -1,10 +0,0 @@
-export const monadicMemoize = fn => {
-  const cache = Object.create(null)
-  return (arg) => {
-    const cacheKey = JSON.stringify(arg)
-    if (cacheKey in cache) {
-      return cache[cacheKey]
-    }
-    return (cache[cacheKey] = fn(arg))
-  }
-}
diff --git a/src/memoize.ts b/src/memoize.ts
new file mode 100644
index 0000000..c3b0387
--- /dev/null
+++ b/src/memoize.ts
@@ -0,0 +1,14 @@
+type MemoizedFunction = <F extends any>(fn: F) => F;
+
+const monadicMemoize: MemoizedFunction = fn => {
+  const cache = Object.create(null);
+  const memoizedFn: any = (arg: unknown) => {
+    const cacheKey = JSON.stringify(arg);
+    if (cacheKey in cache) {
+      return cache[cacheKey];
+    }
+    return (cache[cacheKey] = fn(arg));
+  };
+  return memoizedFn;
+};
+export { monadicMemoize };
diff --git a/src/stores.js b/src/stores.js
deleted file mode 100644
index ff009e5..0000000
--- a/src/stores.js
+++ /dev/null
@@ -1,31 +0,0 @@
-// This was a svelte-only library, it could be a writable store
-class WritableStore {
-  constructor(v) {
-    this._initialValue = v;
-    this._value = this._initialValue;
-    this._subscribers = [];
-  }
-  subscribe(fn) {
-    this._subscribers.push(fn);
-    fn(this._value);
-    return () => this._subscribers.splice(this._subscribers.indexOf(fn), 1);
-  }
-  set(v) {
-    this._value = v;
-    this._subscribers.forEach(fn => fn(v));
-  }
-  update(cb) {
-    this._value = cb(this._value);
-    this._subscribers.forEach(fn => fn(this._value));
-  }
-}
-
-export const currentLocale = new WritableStore();
-export const dictionary = new WritableStore({});
-export const locales = new WritableStore([]);
-dictionary.subscribe(dict => {
-  locales.set(Object.keys(dict));
-});
-export function getCurrentLocale() {
-  return currentLocale._value;
-}
diff --git a/src/stores.ts b/src/stores.ts
new file mode 100644
index 0000000..298656a
--- /dev/null
+++ b/src/stores.ts
@@ -0,0 +1,34 @@
+// This was a svelte-only library, it could be a writable store
+class WritableStore<T> {
+  _value: T;
+  _subscribers: ((T) => void)[];
+  constructor(v) {
+    this._value = v;
+    this._subscribers = [];
+  }
+  subscribe(fn: (value: T) => void) {
+    this._subscribers.push(fn);
+    fn(this._value);
+    return () => this._subscribers.splice(this._subscribers.indexOf(fn), 1);
+  }
+  set(v: T) {
+    this._value = v;
+    this._subscribers.forEach(fn => fn(v));
+  }
+  update(cb: (value: T) => T) {
+    this._value = cb(this._value);
+    this._subscribers.forEach(fn => fn(this._value));
+  }
+}
+export type LocaleDictionary = Record<string, string>;
+/*export */ type Dictionary = Record<string, LocaleDictionary>;
+
+export const currentLocale = new WritableStore<string>(undefined);
+export const dictionary = new WritableStore<Dictionary>({});
+export const locales = new WritableStore<string[]>([]);
+dictionary.subscribe(dict => {
+  locales.set(Object.keys(dict));
+});
+export function getCurrentLocale(): string {
+  return currentLocale._value;
+}
diff --git a/tests/index.test.js b/tests/index.test.js
index 46a5acd..5417de5 100644
--- a/tests/index.test.js
+++ b/tests/index.test.js
@@ -10,7 +10,7 @@ import {
   dictionary,
   locales,
   init
-} from "../src";
+} from "../dist";
 
 beforeEach(() => {
   currentLocale.set(undefined);
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..de97af5
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,14 @@
+{
+  "compilerOptions": {
+    "module": "ESNext",
+    "target": "ESNext",
+    "declaration": true,
+    "outDir": "./dist"
+  },
+  "include": [
+    "src/*"
+  ],
+  "exclude": [
+    "node_modules/**/*"
+  ]
+}
\ No newline at end of file