diff --git a/package.json b/package.json
index e253170..8461f5e 100644
--- a/package.json
+++ b/package.json
@@ -28,7 +28,7 @@
     "lint:fix": "eslint --cache --max-warnings 0 --fix",
     "ensure-linted": "eslint --max-warnings 0 .",
     "semantic-release": "semantic-release",
-    "build": "yarn run clean && rollup -c",
+    "build": "yarn run clean && rollup -c --configPlugin typescript",
     "clean": "rimraf dist",
     "prepare": "husky install"
   },
@@ -44,7 +44,9 @@
     "@semantic-release/changelog": "^5.0.1",
     "@semantic-release/exec": "^5.0.0",
     "@semantic-release/git": "^9.0.0",
+    "@types/glob": "^7.1.4",
     "@types/jest": "^26.0.24",
+    "@types/rimraf": "^3.0.1",
     "@typescript-eslint/eslint-plugin": "^4.28.3",
     "@typescript-eslint/parser": "^4.28.3",
     "babel-jest": "^27.0.6",
diff --git a/rollup.config.js b/rollup.config.ts
similarity index 100%
rename from rollup.config.js
rename to rollup.config.ts
diff --git a/script-modules/gen-pkg.js b/script-modules/gen-pkg.ts
similarity index 54%
rename from script-modules/gen-pkg.js
rename to script-modules/gen-pkg.ts
index 1bcaf87..6d98fca 100644
--- a/script-modules/gen-pkg.js
+++ b/script-modules/gen-pkg.ts
@@ -1,4 +1,4 @@
-function trimDist(p) {
+function trimDist(p: string): string {
   if (!p.startsWith("dist/")) {
     throw new Error("Path should starts with 'dist/'.");
   }
@@ -8,9 +8,11 @@ function trimDist(p) {
 /**
  *
  * @see https://github.com/vladshcherbin/rollup-plugin-generate-package-json#basecontents
- * @param {object} pkg input package.json content
+ * @param pkg input package.json content
  */
-export function getPkgJsonBaseContents(pkg) {
+export function getPkgJsonBaseContents(
+  pkg: Record<string, unknown>,
+): Record<string, unknown> {
   const reserved = [
     "name",
     "version",
@@ -23,14 +25,24 @@ export function getPkgJsonBaseContents(pkg) {
   ];
   const pkgEntries = ["main", "module", "types"];
 
-  const contents = {};
+  const contents: Record<string, unknown> = {};
 
   for (const e of reserved) {
     contents[e] = pkg[e];
   }
 
   for (const e of pkgEntries) {
-    contents[e] = trimDist(pkg[e]);
+    const value = pkg[e];
+    if (value === undefined) continue;
+
+    if (typeof value !== "string") {
+      throw new Error(
+        `package.json "${e}" field must be a string if specified, but received ${String(
+          value,
+        )}`,
+      );
+    }
+    contents[e] = trimDist(value);
   }
 
   contents.exports = {
diff --git a/script-modules/rollup-bundle.js b/script-modules/rollup-bundle.ts
similarity index 53%
rename from script-modules/rollup-bundle.js
rename to script-modules/rollup-bundle.ts
index 8bd2079..107420c 100644
--- a/script-modules/rollup-bundle.js
+++ b/script-modules/rollup-bundle.ts
@@ -1,39 +1,37 @@
 import { compilePlugins } from "./rollup-common";
 import { terser } from "rollup-plugin-terser";
 import { pascalCase } from "pascal-case";
-import pkg from "../package.json";
+import * as pkg from "../package.json";
 import commonjs from "@rollup/plugin-commonjs";
 import { nodeResolve } from "@rollup/plugin-node-resolve";
+import type { ModuleFormat, OutputOptions, RollupOptions } from "rollup";
 
 const GLOBAL_NAMESPACE = pascalCase(pkg.name);
 
-const FORMATS = [
+const FORMATS: ModuleFormat[] = [
   //
   "es",
   "iife",
   "umd",
 ];
 
-/**
- *
- * @param { import("rollup").ModuleFormat } format
- * @returns { import("rollup").OutputOptions }
- */
-function genOutputs(format) {
+function genOutputs(format: ModuleFormat): OutputOptions[] {
   // https://rollupjs.org/guide/en/#outputname
   const name = format === "es" ? undefined : GLOBAL_NAMESPACE;
 
-  return [true, false].map((min) => ({
-    format,
-    sourcemap: true,
-    file: `dist/bundle/${format}${min ? ".min" : ""}.js`,
-    name,
-    plugins: min ? [terser()] : undefined,
-    exports: "auto",
-  }));
+  return [true, false].map(
+    (min): OutputOptions => ({
+      format,
+      sourcemap: true,
+      file: `dist/bundle/${format}${min ? ".min" : ""}.js`,
+      name,
+      plugins: min ? [terser()] : undefined,
+      exports: "auto",
+    }),
+  );
 }
 
-export default {
+const bundleConfig: RollupOptions = {
   input: "src/index.ts",
   output: FORMATS.map(genOutputs).flat(1),
   plugins: [
@@ -43,3 +41,5 @@ export default {
     commonjs(),
   ],
 };
+
+export default bundleConfig;
diff --git a/script-modules/rollup-common.js b/script-modules/rollup-common.js
deleted file mode 100644
index 085aa97..0000000
--- a/script-modules/rollup-common.js
+++ /dev/null
@@ -1,21 +0,0 @@
-import typescript from "@rollup/plugin-typescript";
-import babel from "@rollup/plugin-babel";
-
-export function compilePlugins(options) {
-  return [
-    // https://github.com/rollup/plugins/tree/master/packages/typescript
-    typescript({
-      tsconfig: "tsconfig.json",
-      sourceMap: true,
-      inlineSources: true,
-      ...(options || {}).typescript,
-    }),
-    // https://github.com/rollup/plugins/tree/master/packages/babel
-    babel({
-      extensions: [".js", ".jsx", ".es6", ".es", ".mjs", ".ts", ".tsx"],
-      babelHelpers: "bundled",
-      exclude: /node_modules/,
-      ...(options || {}).babel,
-    }),
-  ];
-}
diff --git a/script-modules/rollup-common.ts b/script-modules/rollup-common.ts
new file mode 100644
index 0000000..85c3858
--- /dev/null
+++ b/script-modules/rollup-common.ts
@@ -0,0 +1,29 @@
+import typescript, { RollupTypescriptOptions } from "@rollup/plugin-typescript";
+import babel, { RollupBabelInputPluginOptions } from "@rollup/plugin-babel";
+import type { Plugin } from "rollup";
+
+export interface CompilePluginsOptions {
+  typescript?: Partial<RollupTypescriptOptions>;
+  babel?: Partial<RollupBabelInputPluginOptions>;
+}
+
+export function compilePlugins(options: CompilePluginsOptions = {}): Plugin[] {
+  return [
+    // https://github.com/rollup/plugins/tree/master/packages/typescript
+    typescript({
+      tsconfig: "tsconfig.json",
+      sourceMap: true,
+      inlineSources: true,
+      include: "src/**/*.ts",
+      exclude: ["**/*.spec.ts", "**/*.test.ts", "**/__test__/**/*.spec.ts"],
+      ...options.typescript,
+    }),
+    // https://github.com/rollup/plugins/tree/master/packages/babel
+    babel({
+      extensions: [".js", ".jsx", ".es6", ".es", ".mjs", ".ts", ".tsx"],
+      babelHelpers: "bundled",
+      exclude: /node_modules/,
+      ...options.babel,
+    }),
+  ];
+}
diff --git a/script-modules/rollup-dts.js b/script-modules/rollup-dts.ts
similarity index 51%
rename from script-modules/rollup-dts.js
rename to script-modules/rollup-dts.ts
index cce9071..ce08968 100644
--- a/script-modules/rollup-dts.js
+++ b/script-modules/rollup-dts.ts
@@ -2,34 +2,47 @@ import dts from "rollup-plugin-dts";
 import getEntryFiles from "./util/entry-files";
 import { chunkFileNames, typescriptDeclarationDir } from "./util/common";
 import rimraf from "rimraf";
+import type { PluginImpl, RollupOptions } from "rollup";
 
-/** @type {import('rollup').PluginImpl} */
-const cleanAfterBuild = (paths) => {
+function isStringOrStringArray(value: unknown): value is string | string[] {
+  return (
+    typeof value === "string" ||
+    (Array.isArray(value) && value.every((v) => typeof v === "string"))
+  );
+}
+
+const cleanAfterBuild: PluginImpl<{ paths?: string | string[] }> = ({
+  paths,
+} = {}) => {
   if (!paths) throw new Error("paths must be specified");
 
-  if (typeof paths === "string") paths = [paths];
+  if (!isStringOrStringArray(paths))
+    throw new Error("paths must be a string or array of strings");
+
+  const pathList = typeof paths === "string" ? [paths] : paths;
 
   return {
     name: "clean-after-build",
     buildEnd() {
       return Promise.all(
-        paths.map(
+        pathList.map(
           (path) =>
-            new Promise((resolve, reject) => {
+            new Promise<void>((resolve, reject) => {
+              // eslint-disable-next-line @typescript-eslint/no-unsafe-call
               rimraf(path, (err) => {
                 if (err) reject(err);
                 else resolve();
               });
             }),
         ),
-      );
+      ).then(() => undefined);
     },
   };
 };
 
 const declarationDir = `dist/es/${typescriptDeclarationDir}/`;
 
-export default {
+const dtsConfig: RollupOptions = {
   input: getEntryFiles((k, v) => [
     k,
     v.replace(/^src\//, declarationDir).replace(/.ts$/, ".d.ts"),
@@ -38,6 +51,7 @@ export default {
     {
       dir: "dist",
       format: "es",
+      // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
       chunkFileNames: (info) => {
         const name = info.name.replace(/\.d$/, "");
         return chunkFileNames
@@ -46,5 +60,7 @@ export default {
       },
     },
   ],
-  plugins: [dts(), cleanAfterBuild(declarationDir)],
+  plugins: [dts(), cleanAfterBuild({ paths: declarationDir })],
 };
+
+export default dtsConfig;
diff --git a/script-modules/rollup-node.js b/script-modules/rollup-node.ts
similarity index 86%
rename from script-modules/rollup-node.js
rename to script-modules/rollup-node.ts
index 906850f..93e3f99 100644
--- a/script-modules/rollup-node.js
+++ b/script-modules/rollup-node.ts
@@ -4,15 +4,15 @@ import { compilePlugins } from "./rollup-common";
 import { getPkgJsonBaseContents } from "./gen-pkg";
 import getEntryFiles from "./util/entry-files";
 import { chunkFileNames, typescriptDeclarationDir } from "./util/common";
+import type { OutputOptions, RollupOptions } from "rollup";
 
-/** @type { import("rollup").OutputOptions } */
-const commonOutputOptions = {
+const commonOutputOptions: Partial<OutputOptions> = {
   exports: "auto",
   sourcemap: true,
   chunkFileNames,
 };
 
-export default {
+const nodeConfig: RollupOptions = {
   input: getEntryFiles(),
   output: [
     { ...commonOutputOptions, dir: "dist", format: "cjs" },
@@ -40,3 +40,5 @@ export default {
     }),
   ],
 };
+
+export default nodeConfig;
diff --git a/script-modules/rollup-shims.d.ts b/script-modules/rollup-shims.d.ts
new file mode 100644
index 0000000..2fb6368
--- /dev/null
+++ b/script-modules/rollup-shims.d.ts
@@ -0,0 +1,4 @@
+declare module "rollup-plugin-generate-package-json" {
+  const generatePackageJson: import("rollup").PluginImpl;
+  export default generatePackageJson;
+}
diff --git a/script-modules/util/common.js b/script-modules/util/common.ts
similarity index 100%
rename from script-modules/util/common.js
rename to script-modules/util/common.ts
diff --git a/script-modules/util/entry-files.js b/script-modules/util/entry-files.js
deleted file mode 100644
index 2623370..0000000
--- a/script-modules/util/entry-files.js
+++ /dev/null
@@ -1,27 +0,0 @@
-import glob from "glob";
-import path from "path";
-
-/**
- *
- * @param { (moduleName: string, fileRelativePath: string, index: number)=> [string, string] } formatter
- * @returns { Record<string, string> }
- */
-export default function getEntryFiles(formatter) {
-  let entries = [
-    ...glob
-      .sync("src/*.ts")
-      .filter((f) => !/(\.(test|spec)\.ts$)|(\/__test__\/)/.test(f))
-      .map((f) => [path.parse(f).name, f]),
-    ...glob
-      .sync("src/*/index.ts")
-      .map((f) => [path.basename(path.dirname(f)), f]),
-  ];
-
-  if (formatter) {
-    entries = entries.map((kv, i) => formatter(kv[0], kv[1], i));
-  }
-
-  const entryFiles = Object.fromEntries(entries);
-
-  return entryFiles;
-}
diff --git a/script-modules/util/entry-files.ts b/script-modules/util/entry-files.ts
new file mode 100644
index 0000000..6df0209
--- /dev/null
+++ b/script-modules/util/entry-files.ts
@@ -0,0 +1,30 @@
+import * as glob from "glob";
+import * as path from "path";
+
+export type EntryFileFormatter = (
+  moduleName: string,
+  fileRelativePath: string,
+  index: number,
+) => [string, string];
+
+export default function getEntryFiles(
+  formatter?: EntryFileFormatter,
+): Record<string, string> {
+  let entries: (readonly [string, string])[] = [
+    ...glob
+      .sync("src/*.ts")
+      .filter((f) => !/(\.(test|spec)\.ts$)|(\/__test__\/)/.test(f))
+      .map((f) => [path.parse(f).name, f] as const),
+    ...glob
+      .sync("src/*/index.ts")
+      .map((f) => [path.basename(path.dirname(f)), f] as const),
+  ];
+
+  if (formatter) {
+    entries = entries.map((kv, i) => formatter(kv[0], kv[1], i));
+  }
+
+  const entryFiles = Object.fromEntries(entries);
+
+  return entryFiles;
+}
diff --git a/tsconfig.json b/tsconfig.json
index ef63518..621857f 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -4,9 +4,11 @@
     "module": "esnext",
     "strict": true,
     "moduleResolution": "node",
+    "resolveJsonModule": true,
+    "allowSyntheticDefaultImports": true,
     "forceConsistentCasingInFileNames": true
   },
-  "include": ["src/**/*.ts", "test/**/*.ts", "scripts/**/*.ts"],
+  "include": ["**/*.ts"],
   "ts-node": {
     "compilerOptions": {
       "skipLibCheck": true,
diff --git a/yarn.lock b/yarn.lock
index 8c742e1..632082d 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1762,6 +1762,14 @@
   resolved "https://registry.yarnpkg.com/@types/estree/-/estree-0.0.39.tgz#e177e699ee1b8c22d23174caaa7422644389509f"
   integrity sha512-EYNwp3bU+98cpU4lAWYYL7Zz+2gryWH1qbdDTidVd6hkiR6weksdbMadyXKXNPEkQFhXM+hVO9ZygomHXp+AIw==
 
+"@types/glob@*", "@types/glob@^7.1.4":
+  version "7.1.4"
+  resolved "https://registry.yarnpkg.com/@types/glob/-/glob-7.1.4.tgz#ea59e21d2ee5c517914cb4bc8e4153b99e566672"
+  integrity sha512-w+LsMxKyYQm347Otw+IfBXOv9UWVjpHpCDdbBMt8Kz/xbvCYNjP+0qPh91Km3iKfSRLBB0P7fAMf0KHrPu+MyA==
+  dependencies:
+    "@types/minimatch" "*"
+    "@types/node" "*"
+
 "@types/graceful-fs@^4.1.2":
   version "4.1.3"
   resolved "https://registry.yarnpkg.com/@types/graceful-fs/-/graceful-fs-4.1.3.tgz#039af35fe26bec35003e8d86d2ee9c586354348f"
@@ -1801,6 +1809,11 @@
   resolved "https://registry.yarnpkg.com/@types/json-schema/-/json-schema-7.0.8.tgz#edf1bf1dbf4e04413ca8e5b17b3b7d7d54b59818"
   integrity sha512-YSBPTLTVm2e2OoQIDYx8HaeWJ5tTToLH67kXR7zYNGupXMEHa2++G8k+DczX2cFVgalypqtyZIcU19AFcmOpmg==
 
+"@types/minimatch@*":
+  version "3.0.5"
+  resolved "https://registry.yarnpkg.com/@types/minimatch/-/minimatch-3.0.5.tgz#1001cc5e6a3704b83c236027e77f2f58ea010f40"
+  integrity sha512-Klz949h02Gz2uZCMGwDUSDS1YBlTdDDgbWHi+81l29tQALUtvz4rAYi5uoVhE5Lagoq6DeqAUlbrHvW/mXDgdQ==
+
 "@types/minimist@^1.2.0":
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/@types/minimist/-/minimist-1.2.0.tgz#69a23a3ad29caf0097f06eda59b361ee2f0639f6"
@@ -1838,6 +1851,14 @@
   resolved "https://registry.yarnpkg.com/@types/retry/-/retry-0.12.0.tgz#2b35eccfcee7d38cd72ad99232fbd58bffb3c84d"
   integrity sha512-wWKOClTTiizcZhXnPY4wikVAwmdYHp8q6DmC+EJUzAMsycb7HB32Kh9RN4+0gExjmPmZSAQjgURXIGATPegAvA==
 
+"@types/rimraf@^3.0.1":
+  version "3.0.1"
+  resolved "https://registry.yarnpkg.com/@types/rimraf/-/rimraf-3.0.1.tgz#1bbc106f0978742289103e080d4b41b3b4656e58"
+  integrity sha512-CAoSlbco40aKZ0CkelBF2g3JeN6aioRaTVnqSX5pWsn/WApm6IDxI4e4tD9D0dY/meCkyyleP1IQDVN13F4maA==
+  dependencies:
+    "@types/glob" "*"
+    "@types/node" "*"
+
 "@types/stack-utils@^2.0.0":
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/@types/stack-utils/-/stack-utils-2.0.1.tgz#20f18294f797f2209b5f65c8e3b5c8e8261d127c"