diff --git a/lib/lru.d.ts b/lib/lru.d.ts
deleted file mode 100644
index 204d0ee..0000000
--- a/lib/lru.d.ts
+++ /dev/null
@@ -1,18 +0,0 @@
-declare class LRU<T = any> {
-    private first;
-    private items;
-    private last;
-    private max;
-    private size;
-    private ttl;
-    constructor(max?: number, ttl?: number);
-    has(key: string): boolean;
-    clear(): this;
-    delete(key: string): this;
-    evict(): this;
-    get(key: string): T;
-    keys(): string[];
-    set(key: string, value: T, bypass?: boolean): this;
-}
-export default function factory(max?: number, ttl?: number): LRU<any>;
-export {};
diff --git a/lib/tiny-lru.cjs.js b/lib/tiny-lru.cjs.js
index 50be73a..712da54 100644
--- a/lib/tiny-lru.cjs.js
+++ b/lib/tiny-lru.cjs.js
@@ -1,120 +1,151 @@
 'use strict';
 
-class LRU {
-    constructor(max = 0, ttl = 0) {
-        this.first = null;
-        this.items = {};
-        this.last = null;
-        this.max = max;
-        this.size = 0;
-        this.ttl = ttl;
-    }
-    has(key) {
-        return key in this.items;
-    }
-    clear() {
-        this.first = null;
-        this.items = {};
-        this.last = null;
-        this.size = 0;
-        return this;
-    }
-    delete(key) {
-        if (this.has(key)) {
-            const item = this.items[key];
-            delete this.items[key];
-            this.size--;
-            if (item.prev !== null) {
-                item.prev.next = item.next;
-            }
-            if (item.next !== null) {
-                item.next.prev = item.prev;
-            }
-            if (this.first === item) {
-                this.first = item.next;
-            }
-            if (this.last === item) {
-                this.last = item.prev;
-            }
-        }
-        return this;
-    }
-    evict() {
-        const item = this.first;
-        delete this.items[item.key];
-        this.first = item.next;
-        this.first.prev = null;
-        this.size--;
-        return this;
-    }
-    get(key) {
-        let result;
-        if (this.has(key)) {
-            const item = this.items[key];
-            if (this.ttl > 0 && item.expiry <= new Date().getTime()) {
-                this.delete(key);
-            }
-            else {
-                result = item.value;
-                this.set(key, result, true);
-            }
-        }
-        return result;
-    }
-    keys() {
-        return Object.keys(this.items);
-    }
-    set(key, value, bypass = false) {
-        let item;
-        if (bypass || this.has(key)) {
-            item = this.items[key];
-            item.value = value;
-            if (this.last !== item) {
-                const last = this.last, next = item.next, prev = item.prev;
-                if (this.first === item) {
-                    this.first = item.next;
-                }
-                item.next = null;
-                item.prev = this.last;
-                last.next = item;
-                if (prev !== null) {
-                    prev.next = next;
-                }
-                if (next !== null) {
-                    next.prev = prev;
-                }
-            }
-        }
-        else {
-            if (this.max > 0 && this.size === this.max) {
-                this.evict();
-            }
-            item = this.items[key] = {
-                expiry: this.ttl > 0 ? new Date().getTime() + this.ttl : this.ttl,
-                key: key,
-                prev: this.last,
-                next: null,
-                value
-            };
-            if (++this.size === 1) {
-                this.first = item;
-            }
-            else {
-                this.last.next = item;
-            }
-        }
-        this.last = item;
-        return this;
-    }
-}
-function factory(max = 1000, ttl = 0) {
-    if (isNaN(max) || max < 0) {
-        throw new TypeError("Invalid max value");
-    }
-    if (isNaN(ttl) || ttl < 0) {
-        throw new TypeError("Invalid ttl value");
-    }
-    return new LRU(max, ttl);
-}
+class LRU {
+		constructor (max = 0, ttl = 0) {
+			this.first = null;
+			this.items = {};
+			this.last = null;
+			this.max = max;
+			this.size = 0;
+			this.ttl = ttl;
+		}
+
+		has (key) {
+			return key in this.items;
+		}
+
+		clear () {
+			this.first = null;
+			this.items = {};
+			this.last = null;
+			this.size = 0;
+
+			return this;
+		}
+
+		delete (key) {
+			if (this.has(key)) {
+				const item = this.items[key];
+
+				delete this.items[key];
+				this.size--;
+
+				if (item.prev !== null) {
+					item.prev.next = item.next;
+				}
+
+				if (item.next !== null) {
+					item.next.prev = item.prev;
+				}
+
+				if (this.first === item) {
+					this.first = item.next;
+				}
+
+				if (this.last === item) {
+					this.last = item.prev;
+				}
+			}
+
+			return this;
+		}
+
+		evict () {
+			const item = this.first;
+
+			delete this.items[item.key];
+			this.first = item.next;
+			this.first.prev = null;
+			this.size--;
+
+			return this;
+		}
+
+		get (key) {
+			let result;
+
+			if (this.has(key)) {
+				const item = this.items[key];
+
+				if (this.ttl > 0 && item.expiry <= new Date().getTime()) {
+					this.delete(key);
+				} else {
+					result = item.value;
+					this.set(key, result, true);
+				}
+			}
+
+			return result;
+		}
+
+		keys () {
+			return Object.keys(this.items);
+		}
+
+		set (key, value, bypass = false) {
+			let item;
+
+			if (bypass || this.has(key)) {
+				item = this.items[key];
+				item.value = value;
+
+				if (this.last !== item) {
+					const last = this.last,
+						next = item.next,
+						prev = item.prev;
+
+					if (this.first === item) {
+						this.first = item.next;
+					}
+
+					item.next = null;
+					item.prev = this.last;
+					last.next = item;
+
+					if (prev !== null) {
+						prev.next = next;
+					}
+
+					if (next !== null) {
+						next.prev = prev;
+					}
+				}
+			} else {
+				if (this.max > 0 && this.size === this.max) {
+					this.evict();
+				}
+
+				item = this.items[key] = {
+					expiry: this.ttl > 0 ? new Date().getTime() + this.ttl : this.ttl,
+					key: key,
+					prev: this.last,
+					next: null,
+					value
+				};
+
+				if (++this.size === 1) {
+					this.first = item;
+				} else {
+					this.last.next = item;
+				}
+			}
+
+			this.last = item;
+
+			return this;
+		}
+	}
+
+	function factory (max = 1000, ttl = 0) {
+		if (isNaN(max) || max < 0) {
+			throw new TypeError("Invalid max value");
+		}
+
+		if (isNaN(ttl) || ttl < 0) {
+			throw new TypeError("Invalid ttl value");
+		}
+
+		return new LRU(max, ttl);
+	}
 
 module.exports = factory;
diff --git a/lib/tiny-lru.esm.js b/lib/tiny-lru.esm.js
index b37987e..c14a83f 100644
--- a/lib/tiny-lru.esm.js
+++ b/lib/tiny-lru.esm.js
@@ -1,118 +1,149 @@
-class LRU {
-    constructor(max = 0, ttl = 0) {
-        this.first = null;
-        this.items = {};
-        this.last = null;
-        this.max = max;
-        this.size = 0;
-        this.ttl = ttl;
-    }
-    has(key) {
-        return key in this.items;
-    }
-    clear() {
-        this.first = null;
-        this.items = {};
-        this.last = null;
-        this.size = 0;
-        return this;
-    }
-    delete(key) {
-        if (this.has(key)) {
-            const item = this.items[key];
-            delete this.items[key];
-            this.size--;
-            if (item.prev !== null) {
-                item.prev.next = item.next;
-            }
-            if (item.next !== null) {
-                item.next.prev = item.prev;
-            }
-            if (this.first === item) {
-                this.first = item.next;
-            }
-            if (this.last === item) {
-                this.last = item.prev;
-            }
-        }
-        return this;
-    }
-    evict() {
-        const item = this.first;
-        delete this.items[item.key];
-        this.first = item.next;
-        this.first.prev = null;
-        this.size--;
-        return this;
-    }
-    get(key) {
-        let result;
-        if (this.has(key)) {
-            const item = this.items[key];
-            if (this.ttl > 0 && item.expiry <= new Date().getTime()) {
-                this.delete(key);
-            }
-            else {
-                result = item.value;
-                this.set(key, result, true);
-            }
-        }
-        return result;
-    }
-    keys() {
-        return Object.keys(this.items);
-    }
-    set(key, value, bypass = false) {
-        let item;
-        if (bypass || this.has(key)) {
-            item = this.items[key];
-            item.value = value;
-            if (this.last !== item) {
-                const last = this.last, next = item.next, prev = item.prev;
-                if (this.first === item) {
-                    this.first = item.next;
-                }
-                item.next = null;
-                item.prev = this.last;
-                last.next = item;
-                if (prev !== null) {
-                    prev.next = next;
-                }
-                if (next !== null) {
-                    next.prev = prev;
-                }
-            }
-        }
-        else {
-            if (this.max > 0 && this.size === this.max) {
-                this.evict();
-            }
-            item = this.items[key] = {
-                expiry: this.ttl > 0 ? new Date().getTime() + this.ttl : this.ttl,
-                key: key,
-                prev: this.last,
-                next: null,
-                value
-            };
-            if (++this.size === 1) {
-                this.first = item;
-            }
-            else {
-                this.last.next = item;
-            }
-        }
-        this.last = item;
-        return this;
-    }
-}
-function factory(max = 1000, ttl = 0) {
-    if (isNaN(max) || max < 0) {
-        throw new TypeError("Invalid max value");
-    }
-    if (isNaN(ttl) || ttl < 0) {
-        throw new TypeError("Invalid ttl value");
-    }
-    return new LRU(max, ttl);
-}
+class LRU {
+		constructor (max = 0, ttl = 0) {
+			this.first = null;
+			this.items = {};
+			this.last = null;
+			this.max = max;
+			this.size = 0;
+			this.ttl = ttl;
+		}
+
+		has (key) {
+			return key in this.items;
+		}
+
+		clear () {
+			this.first = null;
+			this.items = {};
+			this.last = null;
+			this.size = 0;
+
+			return this;
+		}
+
+		delete (key) {
+			if (this.has(key)) {
+				const item = this.items[key];
+
+				delete this.items[key];
+				this.size--;
+
+				if (item.prev !== null) {
+					item.prev.next = item.next;
+				}
+
+				if (item.next !== null) {
+					item.next.prev = item.prev;
+				}
+
+				if (this.first === item) {
+					this.first = item.next;
+				}
+
+				if (this.last === item) {
+					this.last = item.prev;
+				}
+			}
+
+			return this;
+		}
+
+		evict () {
+			const item = this.first;
+
+			delete this.items[item.key];
+			this.first = item.next;
+			this.first.prev = null;
+			this.size--;
+
+			return this;
+		}
+
+		get (key) {
+			let result;
+
+			if (this.has(key)) {
+				const item = this.items[key];
+
+				if (this.ttl > 0 && item.expiry <= new Date().getTime()) {
+					this.delete(key);
+				} else {
+					result = item.value;
+					this.set(key, result, true);
+				}
+			}
+
+			return result;
+		}
+
+		keys () {
+			return Object.keys(this.items);
+		}
+
+		set (key, value, bypass = false) {
+			let item;
+
+			if (bypass || this.has(key)) {
+				item = this.items[key];
+				item.value = value;
+
+				if (this.last !== item) {
+					const last = this.last,
+						next = item.next,
+						prev = item.prev;
+
+					if (this.first === item) {
+						this.first = item.next;
+					}
+
+					item.next = null;
+					item.prev = this.last;
+					last.next = item;
+
+					if (prev !== null) {
+						prev.next = next;
+					}
+
+					if (next !== null) {
+						next.prev = prev;
+					}
+				}
+			} else {
+				if (this.max > 0 && this.size === this.max) {
+					this.evict();
+				}
+
+				item = this.items[key] = {
+					expiry: this.ttl > 0 ? new Date().getTime() + this.ttl : this.ttl,
+					key: key,
+					prev: this.last,
+					next: null,
+					value
+				};
+
+				if (++this.size === 1) {
+					this.first = item;
+				} else {
+					this.last.next = item;
+				}
+			}
+
+			this.last = item;
+
+			return this;
+		}
+	}
+
+	function factory (max = 1000, ttl = 0) {
+		if (isNaN(max) || max < 0) {
+			throw new TypeError("Invalid max value");
+		}
+
+		if (isNaN(ttl) || ttl < 0) {
+			throw new TypeError("Invalid ttl value");
+		}
+
+		return new LRU(max, ttl);
+	}
 
 export default factory;
diff --git a/package-lock.json b/package-lock.json
index d4d145c..df4fee9 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -14,18 +14,18 @@
       }
     },
     "@babel/core": {
-      "version": "7.6.4",
-      "resolved": "https://registry.npmjs.org/@babel/core/-/core-7.6.4.tgz",
-      "integrity": "sha512-Rm0HGw101GY8FTzpWSyRbki/jzq+/PkNQJ+nSulrdY6gFGOsNseCqD6KHRYe2E+EdzuBdr2pxCp6s4Uk6eJ+XQ==",
+      "version": "7.6.2",
+      "resolved": "https://registry.npmjs.org/@babel/core/-/core-7.6.2.tgz",
+      "integrity": "sha512-l8zto/fuoZIbncm+01p8zPSDZu/VuuJhAfA7d/AbzM09WR7iVhavvfNDYCNpo1VvLk6E6xgAoP9P+/EMJHuRkQ==",
       "dev": true,
       "requires": {
         "@babel/code-frame": "^7.5.5",
-        "@babel/generator": "^7.6.4",
+        "@babel/generator": "^7.6.2",
         "@babel/helpers": "^7.6.2",
-        "@babel/parser": "^7.6.4",
+        "@babel/parser": "^7.6.2",
         "@babel/template": "^7.6.0",
-        "@babel/traverse": "^7.6.3",
-        "@babel/types": "^7.6.3",
+        "@babel/traverse": "^7.6.2",
+        "@babel/types": "^7.6.0",
         "convert-source-map": "^1.1.0",
         "debug": "^4.1.0",
         "json5": "^2.1.0",
@@ -33,54 +33,6 @@
         "resolve": "^1.3.2",
         "semver": "^5.4.1",
         "source-map": "^0.5.0"
-      },
-      "dependencies": {
-        "@babel/generator": {
-          "version": "7.6.4",
-          "resolved": "https://registry.npmjs.org/@babel/generator/-/generator-7.6.4.tgz",
-          "integrity": "sha512-jsBuXkFoZxk0yWLyGI9llT9oiQ2FeTASmRFE32U+aaDTfoE92t78eroO7PTpU/OrYq38hlcDM6vbfLDaOLy+7w==",
-          "dev": true,
-          "requires": {
-            "@babel/types": "^7.6.3",
-            "jsesc": "^2.5.1",
-            "lodash": "^4.17.13",
-            "source-map": "^0.5.0"
-          }
-        },
-        "@babel/parser": {
-          "version": "7.6.4",
-          "resolved": "https://registry.npmjs.org/@babel/parser/-/parser-7.6.4.tgz",
-          "integrity": "sha512-D8RHPW5qd0Vbyo3qb+YjO5nvUVRTXFLQ/FsDxJU2Nqz4uB5EnUN0ZQSEYpvTIbRuttig1XbHWU5oMeQwQSAA+A==",
-          "dev": true
-        },
-        "@babel/traverse": {
-          "version": "7.6.3",
-          "resolved": "https://registry.npmjs.org/@babel/traverse/-/traverse-7.6.3.tgz",
-          "integrity": "sha512-unn7P4LGsijIxaAJo/wpoU11zN+2IaClkQAxcJWBNCMS6cmVh802IyLHNkAjQ0iYnRS3nnxk5O3fuXW28IMxTw==",
-          "dev": true,
-          "requires": {
-            "@babel/code-frame": "^7.5.5",
-            "@babel/generator": "^7.6.3",
-            "@babel/helper-function-name": "^7.1.0",
-            "@babel/helper-split-export-declaration": "^7.4.4",
-            "@babel/parser": "^7.6.3",
-            "@babel/types": "^7.6.3",
-            "debug": "^4.1.0",
-            "globals": "^11.1.0",
-            "lodash": "^4.17.13"
-          }
-        },
-        "@babel/types": {
-          "version": "7.6.3",
-          "resolved": "https://registry.npmjs.org/@babel/types/-/types-7.6.3.tgz",
-          "integrity": "sha512-CqbcpTxMcpuQTMhjI37ZHVgjBkysg5icREQIEZ0eG1yCNwg3oy+5AaLiOKmjsCj6nqOsa6Hf0ObjRVwokb7srA==",
-          "dev": true,
-          "requires": {
-            "esutils": "^2.0.2",
-            "lodash": "^4.17.13",
-            "to-fast-properties": "^2.0.0"
-          }
-        }
       }
     },
     "@babel/generator": {
@@ -168,9 +120,9 @@
       }
     },
     "@babel/runtime": {
-      "version": "7.6.3",
-      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.6.3.tgz",
-      "integrity": "sha512-kq6anf9JGjW8Nt5rYfEuGRaEAaH1mkv3Bbu6rYvLOpPh/RusSJXuKPEAoZ7L7gybZkchE8+NV5g9vKF4AGAtsA==",
+      "version": "7.6.2",
+      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.6.2.tgz",
+      "integrity": "sha512-EXxN64agfUqqIGeEjI5dL5z0Sw0ZwWo1mLTi4mQowCZ42O59b7DRpZAnTC6OqdF28wMBMFKNb/4uFGrVaigSpg==",
       "dev": true,
       "requires": {
         "regenerator-runtime": "^0.13.2"
@@ -663,28 +615,28 @@
       }
     },
     "@nodelib/fs.scandir": {
-      "version": "2.1.3",
-      "resolved": "https://registry.npmjs.org/@nodelib/fs.scandir/-/fs.scandir-2.1.3.tgz",
-      "integrity": "sha512-eGmwYQn3gxo4r7jdQnkrrN6bY478C3P+a/y72IJukF8LjB6ZHeB3c+Ehacj3sYeSmUXGlnA67/PmbM9CVwL7Dw==",
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/@nodelib/fs.scandir/-/fs.scandir-2.1.2.tgz",
+      "integrity": "sha512-wrIBsjA5pl13f0RN4Zx4FNWmU71lv03meGKnqRUoCyan17s4V3WL92f3w3AIuWbNnpcrQyFBU5qMavJoB8d27w==",
       "dev": true,
       "requires": {
-        "@nodelib/fs.stat": "2.0.3",
+        "@nodelib/fs.stat": "2.0.2",
         "run-parallel": "^1.1.9"
       }
     },
     "@nodelib/fs.stat": {
-      "version": "2.0.3",
-      "resolved": "https://registry.npmjs.org/@nodelib/fs.stat/-/fs.stat-2.0.3.tgz",
-      "integrity": "sha512-bQBFruR2TAwoevBEd/NWMoAAtNGzTRgdrqnYCc7dhzfoNvqPzLyqlEQnzZ3kVnNrSp25iyxE00/3h2fqGAGArA==",
+      "version": "2.0.2",
+      "resolved": "https://registry.npmjs.org/@nodelib/fs.stat/-/fs.stat-2.0.2.tgz",
+      "integrity": "sha512-z8+wGWV2dgUhLqrtRYa03yDx4HWMvXKi1z8g3m2JyxAx8F7xk74asqPk5LAETjqDSGLFML/6CDl0+yFunSYicw==",
       "dev": true
     },
     "@nodelib/fs.walk": {
-      "version": "1.2.4",
-      "resolved": "https://registry.npmjs.org/@nodelib/fs.walk/-/fs.walk-1.2.4.tgz",
-      "integrity": "sha512-1V9XOY4rDW0rehzbrcqAmHnz8e7SKvX27gh8Gt2WgB0+pdzdiLV83p72kZPU+jvMbS1qU5mauP2iOvO8rhmurQ==",
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@@ -5263,6 +5211,12 @@
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@@ -5956,12 +5910,12 @@
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@@ -7112,63 +7066,40 @@
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+        "rollup": "^1.21.4",
+        "rollup-plugin-add-shebang": "^0.3.1",
+        "rollup-plugin-commonjs": "^10.1.0",
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+        "rollup-plugin-livereload": "^1.0.3",
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+        "rollup-plugin-terser": "^5.1.2",
+        "rollup-plugin-typescript2": "^0.24.3",
+        "ts-jest": "^24.1.0",
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+        "tslint": "^5.20.0",
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@@ -7277,6 +7208,12 @@
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+      "resolved": "https://registry.npmjs.org/ultron/-/ultron-1.0.2.tgz",
+      "integrity": "sha1-rOEWq1V80Zc4ak6I9GhTeMiy5Po=",
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       "resolved": "https://registry.npmjs.org/unicode-length/-/unicode-length-1.0.3.tgz",
diff --git a/package.json b/package.json
index bb6e887..ba49842 100644
--- a/package.json
+++ b/package.json
@@ -16,11 +16,11 @@
     "*.d.ts"
   ],
   "license": "BSD-3-Clause",
-  "source": "src/lru.ts",
+  "source": "src/lru.js",
   "browser": "lib/tiny-lru.js",
   "main": "lib/tiny-lru.cjs.js",
   "module": "lib/tiny-lru.esm.js",
-  "types": "lib/tiny-lru.d.ts",
+  "types": "tiny-lru.d.ts",
   "engines": {
     "node": ">=6"
   },
@@ -33,7 +33,7 @@
   },
   "dependencies": {},
   "devDependencies": {
-    "tslib-cli": "^5.2.3",
+    "tslib-cli": "^5.0.18",
     "nodeunit": "^0.11.3",
     "precise": "^1.1.0"
   },
diff --git a/src/lru.ts b/src/lru.js
similarity index 90%
rename from src/lru.ts
rename to src/lru.js
index 5616f39..62d8367 100644
--- a/src/lru.ts
+++ b/src/lru.js
@@ -1,12 +1,4 @@
-	class LRU<T = any> {
-
-		private first;
-		private items;
-		private last;
-		private max;
-		private size;
-		private ttl;
-
+	class LRU {
 		constructor (max = 0, ttl = 0) {
 			this.first = null;
 			this.items = {};
@@ -16,7 +8,7 @@
 			this.ttl = ttl;
 		}
 
-		has (key: string) {
+		has (key) {
 			return key in this.items;
 		}
 
@@ -29,7 +21,7 @@
 			return this;
 		}
 
-		delete (key: string) {
+		delete (key) {
 			if (this.has(key)) {
 				const item = this.items[key];
 
@@ -67,7 +59,7 @@
 			return this;
 		}
 
-		get (key: string): T {
+		get (key) {
 			let result;
 
 			if (this.has(key)) {
@@ -88,7 +80,7 @@
 			return Object.keys(this.items);
 		}
 
-		set (key: string, value: T, bypass = false) {
+		set (key, value, bypass = false) {
 			let item;
 
 			if (bypass || this.has(key)) {
diff --git a/tiny-lru.d.ts b/tiny-lru.d.ts
new file mode 100644
index 0000000..f4b2f34
--- /dev/null
+++ b/tiny-lru.d.ts
@@ -0,0 +1,14 @@
+declare module "tiny-lru" {
+  export class Lru<T = any> {
+    constructor(max?: number, ttl?: number);
+
+    public has(key: string): boolean;
+    public get(key: string): T;
+    public set(key: string, value: T, bypass?: boolean): this;
+    public clear(): this;
+    public delete(key: string): this;
+    public evict(): this;
+    public keys(): string[];
+  }
+  export default Lru;
+}
diff --git a/tsconfig.json b/tsconfig.json
index 2b5a596..f38ddc4 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,14 +1,13 @@
 {
 	"exclude": ["node_modules", "lib"],
 	"compilerOptions": {
-		"declaration": true,
-		"declarationDir": "lib",
 		"lib": ["dom", "esnext"],
 		"module": "esnext",
 		"moduleResolution": "node",
 		"outDir": "lib",
 		"strict": false,
 		"target": "esnext",
+		"allowJs": true,
 		"sourceMap": true
 	}
 }
\ No newline at end of file