diff --git a/.gitignore b/.gitignore
index bd1c201e..589c761d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,4 @@ bundle.js
 target
 lib
 *.tar.gz
+types
diff --git a/package.json b/package.json
index 8a91f611..b39b0c2d 100644
--- a/package.json
+++ b/package.json
@@ -42,10 +42,10 @@
     "regenerator-runtime": "^0.13.7",
     "rollup-plugin-cleanup": "^3.1.1",
     "serve-static": "^1.13.2",
+    "typescript": "^4.2.3",
     "xxhashjs": "^0.2.2"
   },
   "dependencies": {
-    "rollup": "^2.26.4",
     "@rollup/plugin-commonjs": "^15.0.0",
     "@rollup/plugin-node-resolve": "^9.0.0",
     "aes-js": "^3.1.2",
@@ -54,6 +54,7 @@
     "bs58": "^4.0.1",
     "es6-promise": "https://github.com/bwindels/es6-promise.git#bwindels/expose-flush",
     "olm": "https://packages.matrix.org/npm/olm/olm-3.1.4.tgz",
+    "rollup": "^2.26.4",
     "text-encoding": "^0.7.0"
   }
 }
diff --git a/src/matrix/room/members/MemberList.js b/src/matrix/room/members/MemberList.js
index 734887fd..9241a592 100644
--- a/src/matrix/room/members/MemberList.js
+++ b/src/matrix/room/members/MemberList.js
@@ -18,11 +18,23 @@ import {ObservableMap} from "../../../observable/map/ObservableMap.js";
 
 export class MemberList {
     constructor({members, closeCallback}) {
+        /**
+         * @private
+         * @type {ObservableMap}
+         */
         this._members = new ObservableMap();
         for (const member of members) {
             this._members.add(member.userId, member);
         }
+        /**
+         * @private
+         * @type {Function}
+         */
         this._closeCallback = closeCallback;
+        /**
+         * @private
+         * @type {Number}
+         */
         this._retentionCount = 1;
     }
 
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 00000000..2fb78fa9
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,21 @@
+{
+  "compilerOptions": {
+  	"target": "es2020",
+  	"lib": ["es2020", "dom"],
+  	"allowJs": true,
+  	"checkJs": true,
+    "declaration": true,
+    "emitDeclarationOnly": true,
+    "outDir": "types"
+  },
+  "files": ["src/main.js", "src/platform/web/Platform.js"],
+  "disabledCompilerOptions": {
+  	"noEmit": true,
+    "strict": true,
+    "strictNullChecks": true,
+    "strictFunctionTypes": true,
+    "noImplicitAny": true,
+    "noImplicitReturns": true,
+    "noImplicitThis": true
+  }
+}
diff --git a/yarn.lock b/yarn.lock
index fc6d75d8..19c2b66d 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1014,12 +1014,7 @@ builtin-modules@^3.1.0:
   resolved "https://registry.yarnpkg.com/builtin-modules/-/builtin-modules-3.1.0.tgz#aad97c15131eb76b65b50ef208e7584cd76a7484"
   integrity sha512-k0KL0aWZuBt2lrxrcASWDfwOLMnodeQjodT/1SxEQAXsHANgo6ZC/VEaSEHCXt7aSTZ4/4H5LKa+tBXmW7Vtvw==
 
-caniuse-lite@^1.0.30001111:
-  version "1.0.30001187"
-  resolved "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001187.tgz"
-  integrity sha512-w7/EP1JRZ9552CyrThUnay2RkZ1DXxKe/Q2swTC4+LElLh9RRYrL1Z+27LlakB8kzY0fSmHw9mc7XYDUKAKWMA==
-
-caniuse-lite@^1.0.30001135, caniuse-lite@^1.0.30001137:
+caniuse-lite@^1.0.30001111, caniuse-lite@^1.0.30001135, caniuse-lite@^1.0.30001137:
   version "1.0.30001187"
   resolved "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001187.tgz"
   integrity sha512-w7/EP1JRZ9552CyrThUnay2RkZ1DXxKe/Q2swTC4+LElLh9RRYrL1Z+27LlakB8kzY0fSmHw9mc7XYDUKAKWMA==
@@ -1980,6 +1975,11 @@ toidentifier@1.0.0:
   resolved "https://registry.yarnpkg.com/toidentifier/-/toidentifier-1.0.0.tgz#7e1be3470f1e77948bc43d94a3c8f4d7752ba553"
   integrity sha512-yaOH/Pk/VEhBWWTlhI+qXxDFXlejDGcQipMlyxda9nthulaxLZUNcUqFxokp0vcYnvteJln5FNQDRrxj3YcbVw==
 
+typescript@^4.2.3:
+  version "4.2.3"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-4.2.3.tgz#39062d8019912d43726298f09493d598048c1ce3"
+  integrity sha512-qOcYwxaByStAWrBf4x0fibwZvMRG+r4cQoTjbPtUlrWjBHbmCAww1i448U0GJ+3cNNEtebDteo/cHOR3xJ4wEw==
+
 unicode-canonical-property-names-ecmascript@^1.0.4:
   version "1.0.4"
   resolved "https://registry.yarnpkg.com/unicode-canonical-property-names-ecmascript/-/unicode-canonical-property-names-ecmascript-1.0.4.tgz#2619800c4c825800efdd8343af7dd9933cbe2818"