diff --git a/.npmignore b/.npmignore
index 20c469a..8e6e23f 100644
--- a/.npmignore
+++ b/.npmignore
@@ -4,3 +4,5 @@ node_modules/
 .gitattributes
 .gitignore
 index.test.js
+src/
+tsconfig.json
diff --git a/global.d.ts b/global.d.ts
index 2f539d1..f80ad18 100644
--- a/global.d.ts
+++ b/global.d.ts
@@ -1,6 +1,8 @@
-import { Timeout, Interval } from "./index.d.ts";
+import { Timeout, Interval } from ".";
 
-interface Date {
-    static Timeout: Timeout;
-    static Interval: Interval;
+interface DateConstructor {
+    Timeout: Timeout;
+    Interval: Interval;
 }
+
+export {};
diff --git a/index.js b/index.js
deleted file mode 100644
index abd6efe..0000000
--- a/index.js
+++ /dev/null
@@ -1,110 +0,0 @@
-function Timeout(callback, time, autoStart = false) {
-    var self = this;
-    this._callback = function () { self.state = 3; callback(); }
-    this.currentTime = time;
-    this._startedAt = 0;
-    this._timeLeft = time;
-    this._timerId = -1;
-    this.state = 0;
-    if (autoStart) this.start();
-};
-Timeout.prototype.start = function start(timeMS) {
-    if (this.state == 3) this.stop();
-    if (arguments.length > 0 && this.state == 0) this.currentTime = timeMS;
-    if (this._timerId == -1) {
-        if (this.state == 2) {
-            this._startedAt = Date.now();
-            this._timerId = setTimeout(this._callback, this._timeLeft);
-            this.state = 1;
-        }
-        else if (this.state == 0) {
-            this._startedAt = Date.now();
-            this._timerId = setTimeout(this._callback, this.currentTime);
-            this.state = 1;
-        }
-    }
-    return this;
-};
-Timeout.prototype.pause = function pause() {
-    if (this.state != 1) return this;
-    clearTimeout(this._timerId);
-    this._timerId = -1;
-    this._timeLeft -= Date.now() - this._startedAt;
-    this.state = 2;
-    return this;
-};
-Timeout.prototype.stop = function stop() {
-    clearTimeout(this._timerId);
-    this._timerId = -1;
-    this._timeLeft = 0;
-    this.state = 0;
-    return this;
-};
-Object.defineProperty(Timeout.prototype, "timeLeft", {
-    get: function () {
-        if (this.state == 0) return 0;
-        return Date.now() - this._startedAt;
-    }
-});
-
-function Interval(callback, time, autoStart = false) {
-    var self = this;
-    this._callback = function () { self._lastTrigger = Date.now(); callback(); };
-    this.currentTime = time;
-    this._lastTrigger = 0;
-    this._timeLeft = time;
-    this._timerId = -1;
-    this.state = 0;
-    this._isInTimeout = false;
-    if (autoStart) this.start();
-};
-Interval.prototype.start = function start(timeMS) {
-    if (arguments.length > 0 && this.state == 0) this.currentTime = timeMS;
-    if (this._timerId == -1) {
-        if (this.state == 2) {
-            this._lastTrigger = Date.now();
-            var self = this;
-            this._timerId = setTimeout(function () {
-                this._isInTimeout = false;
-                this._timerId = setInterval(self._callback, self.currentTime);
-            }, this._timeLeft);
-            this.state = 1;
-            this._isInTimeout = true;
-        }
-        else if (this.state == 0) {
-            this._lastTrigger = Date.now();
-            this._timerId = setInterval(this._callback, this.currentTime);
-            this.state = 1;
-        }
-    }
-    return this;
-};
-Interval.prototype.pause = function pause() {
-    if (this.state != 1) return this;
-    this._isInTimeout ? clearTimeout(this._timerId) : clearInterval(this._timerId);
-    this._timerId = -1;
-    this._timeLeft -= Date.now() - this._lastTrigger;
-    this.state = 2;
-    return this;
-};
-Interval.prototype.stop = function stop() {
-    this._isInTimeout ? clearTimeout(this._timerId) : clearInterval(this._timerId);
-    this._timerId = -1;
-    this._timeLeft = 0;
-    this.state = 0;
-    return this;
-};
-Object.defineProperty(Interval.prototype, "timeLeft", {
-    get: function () {
-        if (this.state == 0) return 0;
-        return Date.now() - this._lastTrigger;
-    }
-});
-
-var TimerState = {};
-TimerState[TimerState["Reset"] = 0] = "Reset";
-TimerState[TimerState["Running"] = 1] = "Running";
-TimerState[TimerState["Paused"] = 2] = "Paused";
-TimerState[TimerState["Done"] = 3] = "Done";
-
-module.exports = { Timeout: Timeout, Interval: Interval, TimerState: TimerState };
diff --git a/index.test.js b/index.test.js
index 6effad8..5107bcd 100644
--- a/index.test.js
+++ b/index.test.js
@@ -1,4 +1,4 @@
-const { Timeout, Interval } = require("date-timeout-interval");
+const { Timeout, Interval } = require(".");
 require('jest');
 
 beforeEach(() => {
diff --git a/package-lock.json b/package-lock.json
index 13d26cd..56f1f38 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -4441,6 +4441,12 @@
         "is-typedarray": "^1.0.0"
       }
     },
+    "typescript": {
+      "version": "4.1.3",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-4.1.3.tgz",
+      "integrity": "sha512-B3ZIOf1IKeH2ixgHhj6la6xdwR9QrLC5d1VKeCSY4tvkqhF2eqd9O7txNlS0PO3GrBAFIdr3L1ndNwteUbZLYg==",
+      "dev": true
+    },
     "union-value": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/union-value/-/union-value-1.0.1.tgz",
diff --git a/package.json b/package.json
index 4173488..4b9a8c6 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
   "name": "date-timeout-interval",
   "version": "1.2.0",
   "description": "Implementation of setTimeout and setInterval with pause",
-  "main": "index.js",
+  "main": "dist/index.js",
   "scripts": {
     "test": "jest"
   },
@@ -16,8 +16,13 @@
     "url": "https://github.com/blaumeise20/date-timeout-interval/issues"
   },
   "homepage": "https://github.com/blaumeise20/date-timeout-interval#readme",
-  "keywords": ["timeout", "date", "interval"],
+  "keywords": [
+    "timeout",
+    "date",
+    "interval"
+  ],
   "devDependencies": {
-    "jest": "^26.6.3"
+    "jest": "^26.6.3",
+    "typescript": "^4.1.3"
   }
 }
diff --git a/src/index.ts b/src/index.ts
new file mode 100644
index 0000000..585754a
--- /dev/null
+++ b/src/index.ts
@@ -0,0 +1,138 @@
+export class Timeout {
+    public state: 0 | 1 | 2 | 3;
+    public currentTime: number;
+    public get timeLeft(): number {
+        if (this.state == 0 || this.state == 3) return 0;
+        return Date.now() - this._startedAt;
+    }
+
+    private _startedAt: number;
+    private _callback: () => void;
+    private _timeLeft: number;
+    private _timerId: number;
+
+    public constructor(callback: () => void, timeMS: number, autoStart?: boolean) {
+        var self = this;
+        this._callback = function () { self.state = 3; callback(); }
+        this.currentTime = timeMS;
+        this._startedAt = 0;
+        this._timeLeft = timeMS;
+        this._timerId = -1;
+        this.state = 0;
+        if (autoStart) this.start();
+    }
+
+    public start(): this;
+    public start(timeMS: number): this;
+    public start(timeMS?: number): this {
+        if (this.state == 3) this.stop();
+        if (arguments.length > 0 && this.state == 0) this.currentTime = timeMS;
+        if (this._timerId == -1) {
+            if (this.state == 2) {
+                this._startedAt = Date.now();
+                this._timerId = <any>setTimeout(this._callback, this._timeLeft);
+                this.state = 1;
+            }
+            else if (this.state == 0) {
+                this._startedAt = Date.now();
+                this._timerId = <any>setTimeout(this._callback, this.currentTime);
+                this.state = 1;
+            }
+        }
+        return this;
+    }
+
+    public pause(): this {
+        if (this.state != 1) return this;
+        clearTimeout(<any>this._timerId);
+        this._timerId = -1;
+        this._timeLeft -= Date.now() - this._startedAt;
+        this.state = 2;
+        return this;
+    }
+
+    public stop(): this {
+        clearTimeout(<any>this._timerId);
+        this._timerId = -1;
+        this._timeLeft = 0;
+        this.state = 0;
+        return this;
+    }
+}
+
+export class Interval {
+    public state: 0 | 1 | 2;
+    public currentTime: number;
+    public get timeLeft(): number {
+        if (this.state == 0) return 0;
+        return Date.now() - this._lastTrigger;
+    }
+
+    private _lastTrigger: number;
+    private _callback: () => void;
+    private _timeLeft: number;
+    private _timerId: number;
+    private _isInTimeout: boolean;
+
+    public constructor(callback: (() => void), timeMS?: number, autoStart?: boolean) {
+        var self = this;
+        this._callback = () => { this._lastTrigger = Date.now(); callback(); };
+        this.currentTime = timeMS;
+        this._lastTrigger = 0;
+        this._timeLeft = timeMS;
+        this._timerId = -1;
+        this.state = 0;
+        this._isInTimeout = false;
+        if (autoStart) this.start();
+    }
+
+    public start(): this;
+    public start(timeMS: number): this;
+    public start(timeMS?: number): this {
+        if (arguments.length > 0 && this.state == 0) this.currentTime = timeMS;
+        if (this._timerId == -1) {
+            if (this.state == 2) {
+                this._lastTrigger = Date.now();
+                var self = this;
+                this._timerId = <any>setTimeout(function () {
+                    this._isInTimeout = false;
+                    this._timerId = setInterval(self._callback, self.currentTime);
+                }, this._timeLeft);
+                this.state = 1;
+                this._isInTimeout = true;
+            }
+            else if (this.state == 0) {
+                this._lastTrigger = Date.now();
+                this._timerId = <any>setInterval(this._callback, this.currentTime);
+                this.state = 1;
+            }
+        }
+        return this;
+    }
+
+    public pause(): this {
+        if (this.state != 1) return this;
+        this._isInTimeout ? clearTimeout(<any>this._timerId) : clearInterval(<any>this._timerId);
+        this._timerId = -1;
+        this._timeLeft -= Date.now() - this._lastTrigger;
+        this.state = 2;
+        return this;
+    }
+
+    public stop(): this {
+        this._isInTimeout ? clearTimeout(<any>this._timerId) : clearInterval(<any>this._timerId);
+        this._timerId = -1;
+        this._timeLeft = 0;
+        this.state = 0;
+        this._isInTimeout = false;
+        return this;
+    }
+}
+
+
+export enum TimerState {
+    Reset = 0,
+    Running = 1,
+    Paused = 2,
+    Done = 3
+}
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..9d3a744
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,17 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "outDir": "dist/",
+        "target": "es5",
+        "lib": [
+            "es2015"
+        ],
+        "noImplicitAny": false,
+        "noImplicitThis": false,
+        "alwaysStrict": true,
+        "strictBindCallApply": true,
+        "strictFunctionTypes": true,
+        "declaration": true
+    },
+    "include": ["src/"]
+}