diff --git a/packages/cli/src/getGitCommitHash.ts b/packages/cli/src/getGitCommitHash.ts
index 3353d60..53c7d09 100644
--- a/packages/cli/src/getGitCommitHash.ts
+++ b/packages/cli/src/getGitCommitHash.ts
@@ -4,7 +4,7 @@ import { execSync } from 'node:child_process'
  * return the current commit hash
  * @returns The git commit hash
  */
-export function getGitCommitHash() {
+export function getGitCommitHash(): string | undefined {
   try {
     const hash = execSync('git rev-parse --short HEAD').toString().replace('\n', '').trim()
     if (hash === 'undefined')
diff --git a/packages/cli/src/getHostProjectPkgVersion.ts b/packages/cli/src/getHostProjectPkgVersion.ts
index c094469..c3488a5 100644
--- a/packages/cli/src/getHostProjectPkgVersion.ts
+++ b/packages/cli/src/getHostProjectPkgVersion.ts
@@ -2,6 +2,6 @@
  * It returns the version of the host project's package.json file
  * @returns version
  */
-export function getHostProjectPkgVersion() {
+export function getHostProjectPkgVersion(): string {
   return process.env.npm_package_version as string
 }
diff --git a/packages/cli/src/isDirector.ts b/packages/cli/src/isDirector.ts
index c2cf9f9..20af3e6 100644
--- a/packages/cli/src/isDirector.ts
+++ b/packages/cli/src/isDirector.ts
@@ -1,6 +1,6 @@
 import fs from 'node:fs/promises'
 
-export async function isDirector(path: string) {
+export async function isDirector(path: string): Promise<boolean> {
   try {
     const stat = await fs.stat(path)
     return stat.isDirectory()
diff --git a/packages/cli/src/isFile.ts b/packages/cli/src/isFile.ts
index 403c1b8..a0d981f 100644
--- a/packages/cli/src/isFile.ts
+++ b/packages/cli/src/isFile.ts
@@ -5,7 +5,7 @@ import fs from 'node:fs/promises'
  * @param {string} path - The path to the file to check.
  * @returns A boolean value.
  */
-export async function isFile(path: string) {
+export async function isFile(path: string): Promise<boolean> {
   try {
     const stat = await fs.stat(path)
     return stat.isFile()
diff --git a/packages/cli/src/pathExists.ts b/packages/cli/src/pathExists.ts
index 5e19ce9..4f05297 100644
--- a/packages/cli/src/pathExists.ts
+++ b/packages/cli/src/pathExists.ts
@@ -5,7 +5,7 @@ import { access } from 'node:fs/promises'
  * @param {string} path - The path to check.
  * @returns A promise that resolves to a boolean.
  */
-export async function pathExists(path: string) {
+export async function pathExists(path: string): Promise<boolean> {
   try {
     await access(path)
     return true
diff --git a/packages/core/src/callLimit.ts b/packages/core/src/callLimit.ts
index 5f155e6..2d38ae1 100644
--- a/packages/core/src/callLimit.ts
+++ b/packages/core/src/callLimit.ts
@@ -18,7 +18,7 @@ import { isFunction, isNumber } from '@utopia-utils/share'
  * ```
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/callLimit.ts
  */
-export function callLimit<T extends (...args: any[]) => any>(fn: T, limit = 1) {
+export function callLimit<T extends (...args: any[]) => any>(fn: T, limit = 1): (this: ThisParameterType<T>, ...args: Parameters<T>) => ReturnType<T> {
   if (!isFunction(fn))
     throw new TypeError('fn expected a function')
 
diff --git a/packages/core/src/capitalize.ts b/packages/core/src/capitalize.ts
index 3aa7ed5..598081d 100644
--- a/packages/core/src/capitalize.ts
+++ b/packages/core/src/capitalize.ts
@@ -4,6 +4,6 @@
  * @returns {string} - The capitalized string.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/capitalize.ts
  */
-export function capitalize<T extends string>(str: T) {
+export function capitalize<T extends string>(str: T): Capitalize<T> {
   return str.charAt(0).toUpperCase() + str.slice(1) as Capitalize<T>
 }
diff --git a/packages/core/src/createEnumFromOptions.ts b/packages/core/src/createEnumFromOptions.ts
index 2d1cee0..2602efe 100644
--- a/packages/core/src/createEnumFromOptions.ts
+++ b/packages/core/src/createEnumFromOptions.ts
@@ -31,7 +31,7 @@
  * ```
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/createEnumFromOptions.ts
  */
-export function createEnumFromOptions<T extends readonly Option[]>(options: T) {
+export function createEnumFromOptions<T extends readonly Option[]>(options: T): MapTuple<T> {
   const res: Record<string, unknown> = {}
   try {
     options.forEach((v) => {
diff --git a/packages/core/src/csv.ts b/packages/core/src/csv.ts
index 73bd988..09d3f15 100644
--- a/packages/core/src/csv.ts
+++ b/packages/core/src/csv.ts
@@ -1,6 +1,6 @@
 import { isArray, isPlainObject } from '@utopia-utils/share'
 
-function escapeDoubleQuotes(val: string) {
+function escapeDoubleQuotes(val: string): string {
   return val.replace(/"/g, '""')
 }
 
@@ -8,7 +8,7 @@ function escapeDoubleQuotes(val: string) {
  * check separator is valid
  * @param {string} separator
  */
-function checkSeparator(separator: string) {
+function checkSeparator(separator: string): void {
   if (!separator)
     throw new Error('The separator cannot be empty')
 
@@ -68,7 +68,7 @@ interface ArrayToCSVOptions<T> {
  * ```
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/csv.ts
  */
-export function arrayToCSV<T extends (any[] | object)>(arr: T[], options: ArrayToCSVOptions<T> = {}) {
+export function arrayToCSV<T extends (any[] | object)>(arr: T[], options: ArrayToCSVOptions<T> = {}): string {
   const { headers, separator = ',', getRow, withPrefix } = options
 
   checkSeparator(separator)
diff --git a/packages/core/src/deepClone.ts b/packages/core/src/deepClone.ts
index 3d6aa63..2e1998c 100644
--- a/packages/core/src/deepClone.ts
+++ b/packages/core/src/deepClone.ts
@@ -1,4 +1,4 @@
-function clone<T>(src: T, seen = new Map()) {
+function clone<T>(src: T, seen = new Map()): T {
   // Immutable things - null, undefined, functions, symbols, etc.
   if (!src || typeof src !== 'object')
     return src
diff --git a/packages/core/src/defineDictionary.ts b/packages/core/src/defineDictionary.ts
index 5c85b84..0bef117 100644
--- a/packages/core/src/defineDictionary.ts
+++ b/packages/core/src/defineDictionary.ts
@@ -107,7 +107,16 @@ type ToValueKey<T> = T extends readonly [infer A, ...infer B]
  * @example
  * ```ts
     // at src/constant.ts
-    const { get_MUSIC_TYPE_KEYS, get_MUSIC_TYPE_KV, get_MUSIC_TYPE_MAP, get_MUSIC_TYPE_MAP_BY_KEY, get_MUSIC_TYPE_MAP_BY_VALUE, get_MUSIC_TYPE_OPTIONS, get_MUSIC_TYPE_VALUES, get_MUSIC_TYPE_VK } = defineDictionary([
+    const {
+      get_MUSIC_TYPE_KEYS,
+      get_MUSIC_TYPE_KV,
+      get_MUSIC_TYPE_MAP,
+      get_MUSIC_TYPE_MAP_BY_KEY,
+      get_MUSIC_TYPE_MAP_BY_VALUE,
+      get_MUSIC_TYPE_OPTIONS,
+      get_MUSIC_TYPE_VALUES,
+      get_MUSIC_TYPE_VK
+    } = defineDictionary([
       {
         key: 'POP',
         value: 1,
diff --git a/packages/core/src/encryptPhone.ts b/packages/core/src/encryptPhone.ts
index f0201ee..4704f90 100644
--- a/packages/core/src/encryptPhone.ts
+++ b/packages/core/src/encryptPhone.ts
@@ -4,6 +4,6 @@
  * @returns The phone number with the middle 4 digits replaced with asterisks.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/encryptPhone.ts
  */
-export function encryptPhone(phone: `${number}`) {
+export function encryptPhone(phone: `${number}`): string {
   return phone.replace(/(\d{3})\d{4}(\d{4})/, '$1****$2')
 }
diff --git a/packages/core/src/escapeStringRegexp.ts b/packages/core/src/escapeStringRegexp.ts
index 8ad6e66..9b43f04 100644
--- a/packages/core/src/escapeStringRegexp.ts
+++ b/packages/core/src/escapeStringRegexp.ts
@@ -5,5 +5,5 @@
  * @param [string] - The string to escape. Defaults to an empty string.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/escapeStringRegexp.ts
  */
-export const escapeStringRegexp = (string = '') =>
+export const escapeStringRegexp = (string = ''): string =>
   string.replace(/[|\\{}()[\]^$+*?.]/g, '\\$&').replace(/-/g, '\\x2d')
diff --git a/packages/core/src/formatNumberThousand.ts b/packages/core/src/formatNumberThousand.ts
index 13be27b..99db3cb 100644
--- a/packages/core/src/formatNumberThousand.ts
+++ b/packages/core/src/formatNumberThousand.ts
@@ -19,7 +19,7 @@ interface Options {
  * ```
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/formatNumberThousand.ts
  */
-export function formatNumberThousand(num: number, options: Options = {}) {
+export function formatNumberThousand(num: number, options: Options = {}): string {
   if (Number.isNaN(num))
     return ''
 
diff --git a/packages/core/src/getFileName.ts b/packages/core/src/getFileName.ts
index ac339bf..347cca9 100644
--- a/packages/core/src/getFileName.ts
+++ b/packages/core/src/getFileName.ts
@@ -6,6 +6,6 @@
  * @returns file name
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/getFileName.ts
  */
-export function getFileName(path: string) {
+export function getFileName(path: string): string {
   return path.replace(/^.*(\\|\/)/, '')
 }
diff --git a/packages/core/src/getQueryParams.ts b/packages/core/src/getQueryParams.ts
index 8872f92..df8d4f1 100644
--- a/packages/core/src/getQueryParams.ts
+++ b/packages/core/src/getQueryParams.ts
@@ -19,7 +19,7 @@ import type { LocationQuery } from './parseQuery'
  * ```
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/getQueryParams.ts
  */
-export function getQueryParams<T extends LocationQuery>(location: string) {
+export function getQueryParams<T extends LocationQuery>(location: string): Partial<T> {
   let query: LocationQuery = {}
 
   const searchPos = location.indexOf('?')
diff --git a/packages/core/src/objectKeys.ts b/packages/core/src/objectKeys.ts
index 5f23b71..4d98e25 100644
--- a/packages/core/src/objectKeys.ts
+++ b/packages/core/src/objectKeys.ts
@@ -1,10 +1,11 @@
+type ObjectKeysReturn<T> = (keyof T & (string | number | boolean | null | undefined))[]
 /**
  * strict type Object.keys()
  * @param {T} obj - T
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/objectKeys.ts
  */
-export function objectKeys<T extends object>(obj: T) {
-  return Object.keys(obj) as (keyof T & (string | number | boolean | null | undefined))[]
+export function objectKeys<T extends object>(obj: T): ObjectKeysReturn<T> {
+  return Object.keys(obj) as ObjectKeysReturn<T>
 }
 
 // const symbol = Symbol('symbol')
diff --git a/packages/core/src/onWindowFocus.ts b/packages/core/src/onWindowFocus.ts
index 53e6a72..a2aa000 100644
--- a/packages/core/src/onWindowFocus.ts
+++ b/packages/core/src/onWindowFocus.ts
@@ -15,7 +15,7 @@ import { debounce } from './vendor'
  * ```
  *
  */
-export function onWindowFocus(callback: (...args: any[]) => any) {
+export function onWindowFocus(callback: (...args: any[]) => any): () => void {
   const listener = debounce(100, callback)
 
   window.addEventListener('focus', listener, false)
diff --git a/packages/core/src/once.ts b/packages/core/src/once.ts
index 14af1b0..bda7536 100644
--- a/packages/core/src/once.ts
+++ b/packages/core/src/once.ts
@@ -15,6 +15,6 @@ import { callLimit } from './callLimit'
  * ```
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/once.ts
  */
-export function once<T extends (...args: any[]) => any>(fn: T) {
+export function once<T extends (...args: any[]) => any>(fn: T): (this: ThisParameterType<T>, ...args: Parameters<T>) => ReturnType<T> {
   return callLimit(fn, 1)
 }
diff --git a/packages/core/src/onlyResolvesLast.ts b/packages/core/src/onlyResolvesLast.ts
index fb73092..59104ea 100644
--- a/packages/core/src/onlyResolvesLast.ts
+++ b/packages/core/src/onlyResolvesLast.ts
@@ -12,7 +12,7 @@
  * ```
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/onlyResolvesLast.ts
  */
-export function onlyResolvesLast<T extends (...args: any) => Promise<any>>(fn: T) {
+export function onlyResolvesLast<T extends (...args: any) => Promise<any>>(fn: T): (this: ThisParameterType<T>, ...args: Parameters<T>) => ReturnType<T> {
   let time = 0
   function wrappedFn(this: ThisParameterType<T>, ...args: Parameters<T>): ReturnType<T> {
     const currentTime = time + 1
diff --git a/packages/core/src/parseQuery.ts b/packages/core/src/parseQuery.ts
index c33c565..a19e4f7 100644
--- a/packages/core/src/parseQuery.ts
+++ b/packages/core/src/parseQuery.ts
@@ -45,7 +45,7 @@ export function decode(text: string | number): string {
     expect(params.sex).toBe(null)
   ```
  */
-export function parseQuery<T extends LocationQuery>(search: string) {
+export function parseQuery<T extends LocationQuery>(search: string): T {
   const query: LocationQuery = {}
   // avoid creating an object with an empty key and empty value
   // because of split('&')
diff --git a/packages/core/src/randomInt.ts b/packages/core/src/randomInt.ts
index 2139842..a86ed4b 100644
--- a/packages/core/src/randomInt.ts
+++ b/packages/core/src/randomInt.ts
@@ -5,6 +5,6 @@
  * @returns A random integer between min and max.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/randomInt.ts
  */
-export function randomInt(max: number, min = 0) {
+export function randomInt(max: number, min = 0): number {
   return Math.floor(Math.random() * (max - min + 1) + min)
 }
diff --git a/packages/core/src/randomString.ts b/packages/core/src/randomString.ts
index 9adcbae..96d9a11 100644
--- a/packages/core/src/randomString.ts
+++ b/packages/core/src/randomString.ts
@@ -6,7 +6,7 @@
  * @returns A random string of the length specified.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/core/src/randomString.ts
  */
-export const randomString = (length: number, chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789') => {
+export const randomString = (length: number, chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'): string => {
   const maxPos = chars.length
   let str = ''
   for (let i = 0; i < length; i++)
diff --git a/packages/core/src/utils.ts b/packages/core/src/utils.ts
deleted file mode 100644
index e69de29..0000000
diff --git a/packages/dom/src/canUseDom.ts b/packages/dom/src/canUseDom.ts
index c6b214c..a02de61 100644
--- a/packages/dom/src/canUseDom.ts
+++ b/packages/dom/src/canUseDom.ts
@@ -3,6 +3,6 @@
  * @returns a boolean value indicating whether the DOM (Document Object Model) can be used.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/dom/src/canUseDom.ts
  */
-export function canUseDom() {
+export function canUseDom(): boolean {
   return !!(typeof window !== 'undefined' && window.document && window.document.createElement)
 }
diff --git a/packages/dom/src/domContains.ts b/packages/dom/src/domContains.ts
index 2c057d8..af20074 100644
--- a/packages/dom/src/domContains.ts
+++ b/packages/dom/src/domContains.ts
@@ -9,7 +9,7 @@
  * otherwise.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/dom/src/contains.ts
  */
-export function domContains(root: Node | null | undefined, n: Node | null) {
+export function domContains(root: Node | null | undefined, n: Node | null): boolean {
   if (!root)
     return false
 
diff --git a/packages/dom/src/dynamicCSS.ts b/packages/dom/src/dynamicCSS.ts
index 0699b90..6a175a9 100644
--- a/packages/dom/src/dynamicCSS.ts
+++ b/packages/dom/src/dynamicCSS.ts
@@ -23,7 +23,7 @@ interface Options {
   mark?: string
 }
 
-function getMark({ mark }: Options = {}) {
+function getMark({ mark }: Options = {}): string {
   if (mark)
     return mark.startsWith('data-') ? mark : `data-${mark}`
 
@@ -48,13 +48,13 @@ function getOrder(prepend?: Prepend): AppendType {
 /**
  * Find style which inject by rc-util
  */
-function findStyles(container: ContainerType) {
+function findStyles(container: ContainerType): HTMLStyleElement[] {
   return Array.from(
     (containerCache.get(container) || container).children,
   ).filter(node => node.tagName === 'STYLE') as HTMLStyleElement[]
 }
 
-export function injectCSS(css: string, option: Options = {}) {
+export function injectCSS(css: string, option: Options = {}): HTMLStyleElement | null {
   if (!canUseDom())
     return null
 
@@ -111,7 +111,7 @@ export function injectCSS(css: string, option: Options = {}) {
   return styleNode
 }
 
-function findExistNode(key: string, option: Options = {}) {
+function findExistNode(key: string, option: Options = {}): HTMLStyleElement | undefined {
   const container = getContainer(option)
 
   return findStyles(container).find(
@@ -119,7 +119,7 @@ function findExistNode(key: string, option: Options = {}) {
   )
 }
 
-export function removeCSS(key: string, option: Options = {}) {
+export function removeCSS(key: string, option: Options = {}): void {
   const existNode = findExistNode(key, option)
   if (existNode) {
     const container = getContainer(option)
@@ -130,7 +130,7 @@ export function removeCSS(key: string, option: Options = {}) {
 /**
  * qiankun will inject `appendChild` to insert into other
  */
-function syncRealContainer(container: ContainerType, option: Options) {
+function syncRealContainer(container: ContainerType, option: Options): void {
   const cachedRealContainer = containerCache.get(container)
 
   // Find real container when not cached or cached container removed
@@ -149,7 +149,7 @@ function syncRealContainer(container: ContainerType, option: Options) {
 /**
  * manually clear container cache to avoid global cache in unit testes
  */
-export function clearContainerCache() {
+export function clearContainerCache(): void {
   containerCache.clear()
 }
 
@@ -166,7 +166,7 @@ export function clearContainerCache() {
  * updateCSS('body { color: red }', 'my-style')
  * ```
  * */
-export function updateCSS(css: string, key: string, option: Options = {}) {
+export function updateCSS(css: string, key: string, option: Options = {}): HTMLStyleElement | undefined {
   const container = getContainer(option)
 
   // Sync real parent
diff --git a/packages/dom/src/isAndroid.ts b/packages/dom/src/isAndroid.ts
index b2c5aec..739d0ec 100644
--- a/packages/dom/src/isAndroid.ts
+++ b/packages/dom/src/isAndroid.ts
@@ -3,7 +3,7 @@
  * @returns A boolean value.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/dom/src/isAndroid.ts
  */
-export function isAndroid() {
+export function isAndroid(): boolean {
   if (typeof navigator === 'undefined')
     return false
   return /android/i.test(navigator.userAgent)
diff --git a/packages/dom/src/isIOS.ts b/packages/dom/src/isIOS.ts
index eaf3bc1..4f3c9b5 100644
--- a/packages/dom/src/isIOS.ts
+++ b/packages/dom/src/isIOS.ts
@@ -3,7 +3,7 @@
  * @returns A boolean value.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/dom/src/isIOS.ts
  */
-export function isIOS() {
+export function isIOS(): boolean {
   if (typeof navigator === 'undefined')
     return false
   return /iPad|iPhone|iPod/.test(navigator.userAgent)
diff --git a/packages/dom/src/isMobile.ts b/packages/dom/src/isMobile.ts
index 67f43ff..b396c20 100644
--- a/packages/dom/src/isMobile.ts
+++ b/packages/dom/src/isMobile.ts
@@ -3,7 +3,7 @@
  * @returns A boolean value.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/dom/src/isMobile.ts
  */
-export function isMobile() {
+export function isMobile(): boolean {
   if (typeof navigator === 'undefined' || typeof window === 'undefined')
     return false
 
diff --git a/packages/dom/src/isWeixin.ts b/packages/dom/src/isWeixin.ts
index 7677799..cc9a75b 100644
--- a/packages/dom/src/isWeixin.ts
+++ b/packages/dom/src/isWeixin.ts
@@ -3,7 +3,7 @@
  * @returns A boolean value.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/dom/src/isWeixin.ts
  */
-export function isWeixin() {
+export function isWeixin(): boolean {
   const ua = navigator.userAgent.toLowerCase()
   return /MicroMessenger/i.test(ua)
 }
diff --git a/packages/dom/src/loadCSS.ts b/packages/dom/src/loadCSS.ts
index 11726dd..eba59a9 100644
--- a/packages/dom/src/loadCSS.ts
+++ b/packages/dom/src/loadCSS.ts
@@ -1,3 +1,6 @@
+/**
+ * Options for {@link loadCSS} function
+ */
 interface LoadCSSOptions {
   /**
    * Media query for styles to apply
@@ -11,6 +14,14 @@ interface LoadCSSOptions {
   attrs?: Record<string, string>
 }
 
+/**
+ * return type of {@link loadCSS} function
+ */
+interface LoadCSSReturn {
+  unload: () => void
+  linkTag: HTMLLinkElement
+}
+
 /**
  * It loads a CSS file into the page
  * @param {string} path - the path to the CSS file
@@ -20,7 +31,7 @@ interface LoadCSSOptions {
  *   - linkTag: the link tag that was created
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/dom/src/loadCSS.ts
  */
-export function loadCSS(path: string, options?: LoadCSSOptions) {
+export function loadCSS(path: string, options?: LoadCSSOptions): LoadCSSReturn {
   const {
     attrs = {},
     media,
@@ -48,7 +59,7 @@ export function loadCSS(path: string, options?: LoadCSSOptions) {
 }
 
 /** remove the script tag */
-function unload(path: string) {
+function unload(path: string): void {
   const linkEl = document.querySelector(`link[href="${path}"]`)
   if (linkEl)
     linkEl.remove()
diff --git a/packages/dom/src/loadScript.ts b/packages/dom/src/loadScript.ts
index fc9dd55..4c62bc4 100644
--- a/packages/dom/src/loadScript.ts
+++ b/packages/dom/src/loadScript.ts
@@ -1,3 +1,6 @@
+/**
+ * options type for {@link loadScript} function
+ */
 interface LoadScriptOptions {
   /**
    * Add `async` attribute to the script tag
@@ -34,6 +37,14 @@ interface LoadScriptOptions {
   onStatusChange?: (status: 'loading' | 'loaded' | 'error') => void
 }
 
+/**
+ * return type of {@link loadScript} function
+ */
+interface LoadScriptReturn {
+  unload: () => void
+  scriptTag: HTMLScriptElement
+}
+
 /**
  * It loads a script tag into the DOM
  * @param {string} src - The URL of the script to load.
@@ -43,7 +54,7 @@ interface LoadScriptOptions {
  *   - scriptTag: the script tag that was created
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/dom/src/loadScript.ts
  */
-export function loadScript(src: string, options?: LoadScriptOptions) {
+export function loadScript(src: string, options?: LoadScriptOptions): LoadScriptReturn {
   const {
     async = true,
     defer,
@@ -100,7 +111,7 @@ export function loadScript(src: string, options?: LoadScriptOptions) {
 }
 
 /** remove the script tag */
-function unload(src: string) {
+function unload(src: string): void {
   const script = document.querySelector(`script[src="${src}"]`)
   if (script)
     script.remove()
diff --git a/packages/dom/src/panzoom/utils.ts b/packages/dom/src/panzoom/utils.ts
index dfd90b3..c090368 100644
--- a/packages/dom/src/panzoom/utils.ts
+++ b/packages/dom/src/panzoom/utils.ts
@@ -1,12 +1,12 @@
 import type { Transform } from './type'
 
-export function getScaleMultiplier(delta: number, zoomFactor: number) {
+export function getScaleMultiplier(delta: number, zoomFactor: number): number {
   const sign = Math.sign(delta)
   const deltaAdjustedSpeed = Math.min(0.25, Math.abs(zoomFactor * delta / 128))
   return 1 - sign * deltaAdjustedSpeed
 }
 
-export function applyTransform(dom: HTMLElement, transform: Transform, cb?: (val: Transform) => void) {
+export function applyTransform(dom: HTMLElement, transform: Transform, cb?: (val: Transform) => void): void {
   dom.style.transformOrigin = '0 0 0'
   dom.style.transform = `matrix(${transform.scale}, 0, 0, ${transform.scale}, ${transform.x}, ${transform.y})`
   cb?.(transform)
diff --git a/packages/dom/src/setCssVar.ts b/packages/dom/src/setCssVar.ts
index 5e1e3d3..6e9fd0d 100644
--- a/packages/dom/src/setCssVar.ts
+++ b/packages/dom/src/setCssVar.ts
@@ -10,7 +10,7 @@ import { isPlainObject } from '@utopia-utils/share'
  * refers to the root element of the current document.
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/dom/src/setCssVar.ts
  */
-export function setCssVar(variables: Record<string, string | null>, root = window?.document?.documentElement) {
+export function setCssVar(variables: Record<string, string | null>, root = window?.document?.documentElement): void {
   if (variables && isPlainObject(variables) && root) {
     Object.keys(variables).forEach((key) => {
       root.style.setProperty(key, variables[key])
diff --git a/packages/dom/src/style.ts b/packages/dom/src/style.ts
index 7942667..35246ab 100644
--- a/packages/dom/src/style.ts
+++ b/packages/dom/src/style.ts
@@ -13,13 +13,13 @@ export const hasClass = (el: Element, cls: string): boolean => {
   return el.classList.contains(cls)
 }
 
-export const addClass = (el: Element, cls: string) => {
+export const addClass = (el: Element, cls: string): void => {
   if (!el || !cls.trim())
     return
   el.classList.add(...classNameToArray(cls))
 }
 
-export const removeClass = (el: Element, cls: string) => {
+export const removeClass = (el: Element, cls: string): void => {
   if (!el || !cls.trim())
     return
   el.classList.remove(...classNameToArray(cls))
diff --git a/packages/dom/src/waitForSelector.ts b/packages/dom/src/waitForSelector.ts
index beeaa97..ebbbeb7 100644
--- a/packages/dom/src/waitForSelector.ts
+++ b/packages/dom/src/waitForSelector.ts
@@ -1,3 +1,6 @@
+/**
+ * Options for {@link waitForSelector}
+ */
 interface WaitForOptions {
   /** Maximum time to wait in milliseconds, default is 30000 (30s) */
   timeoutMillisecond?: number
diff --git a/packages/dom/src/webp.ts b/packages/dom/src/webp.ts
index 20f30f6..9a56cd6 100644
--- a/packages/dom/src/webp.ts
+++ b/packages/dom/src/webp.ts
@@ -4,7 +4,7 @@
  * @returns A promise that resolves to a boolean indicating whether the feature is supported.
  * @link Official way by Google: https://developers.google.com/speed/webp/faq?hl=zh-cn#how_can_i_detect_browser_support_for_webp
  */
-export async function checkWebpFeature(feature: 'lossy' | 'lossless' | 'alpha' | 'animation' = 'lossy') {
+export async function checkWebpFeature(feature: 'lossy' | 'lossless' | 'alpha' | 'animation' = 'lossy'): Promise<boolean> {
   return new Promise<boolean>((resolve) => {
     const kTestImages = {
       lossy: 'UklGRiIAAABXRUJQVlA4IBYAAAAwAQCdASoBAAEADsD+JaQAA3AAAAAA',
@@ -28,6 +28,6 @@ export async function checkWebpFeature(feature: 'lossy' | 'lossless' | 'alpha' |
  * Checks the browser's support for WebP image format.
  * @returns A promise that resolves to a boolean indicating whether WebP is supported.
  */
-export async function checkWebpSupport() {
+export async function checkWebpSupport(): Promise<boolean> {
   return checkWebpFeature('lossy')
 }
diff --git a/packages/share/src/is.ts b/packages/share/src/is.ts
index d5bbc76..3fcdd01 100644
--- a/packages/share/src/is.ts
+++ b/packages/share/src/is.ts
@@ -31,7 +31,7 @@ export const isObject = (val: unknown): val is Record<any, any> =>
 
 export const isWindow = (val: unknown): boolean => typeof window !== 'undefined' && toTypeString(val) === 'Window'
 
-export const isIntegerKey = (key: unknown) =>
+export const isIntegerKey = (key: unknown): boolean =>
   isString(key)
   && key !== 'NaN'
   && key[0] !== '-'
diff --git a/packages/share/src/isNumberLike.ts b/packages/share/src/isNumberLike.ts
index 0e97182..b61020f 100644
--- a/packages/share/src/isNumberLike.ts
+++ b/packages/share/src/isNumberLike.ts
@@ -9,7 +9,7 @@
  * ```
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/share/src/isNumberLike.ts
  */
-export function isNumberLike(val: unknown) {
+export function isNumberLike(val: unknown): boolean {
   return (typeof val === 'number' && !Number.isNaN(val))
     || (typeof val === 'string' && val.trim() !== '' && !Number.isNaN(Number(val)))
 }
diff --git a/packages/share/src/isValidUrl.ts b/packages/share/src/isValidUrl.ts
index 8860101..2794047 100644
--- a/packages/share/src/isValidUrl.ts
+++ b/packages/share/src/isValidUrl.ts
@@ -12,7 +12,7 @@
  * ```
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/share/src/isValidUrl.ts
  */
-export function isValidUrl(urlString: string) {
+export function isValidUrl(urlString: string): boolean {
   try {
     return Boolean(new URL(urlString))
   }
diff --git a/packages/share/src/measurePerformance.ts b/packages/share/src/measurePerformance.ts
index 8188e7f..3cbe7dd 100644
--- a/packages/share/src/measurePerformance.ts
+++ b/packages/share/src/measurePerformance.ts
@@ -1,5 +1,5 @@
 /* eslint-disable no-console */
-export function measurePerformance<T extends (...args: any[]) => any>(this: ThisParameterType<T>, fn: T, ...args: Parameters<T>) {
+export function measurePerformance<T extends (...args: any[]) => any>(this: ThisParameterType<T>, fn: T, ...args: Parameters<T>): number {
   const start = performance.now()
   fn.call(this, ...args)
   const end = performance.now()
diff --git a/packages/tree/src/breadthFirstTraverse.ts b/packages/tree/src/breadthFirstTraverse.ts
index a195014..ca189a0 100644
--- a/packages/tree/src/breadthFirstTraverse.ts
+++ b/packages/tree/src/breadthFirstTraverse.ts
@@ -34,7 +34,7 @@ interface Options {
     // output 'a', 'c', 'b'
   * ```
  */
-export function breadthFirstTraverse<TreeNode>(tree: TreeNode[] | TreeNode, action: (node: TreeNode) => unknown, options?: Options) {
+export function breadthFirstTraverse<TreeNode>(tree: TreeNode[] | TreeNode, action: (node: TreeNode) => unknown, options?: Options): void {
   if (!isFunction(action))
     throw new Error('traverse action should be a function')
 
diff --git a/packages/tree/src/buildTreeFromList.ts b/packages/tree/src/buildTreeFromList.ts
index b926f64..a03b792 100644
--- a/packages/tree/src/buildTreeFromList.ts
+++ b/packages/tree/src/buildTreeFromList.ts
@@ -43,7 +43,7 @@ interface Options {
     })
  * ```
  */
-export function buildTreeFromList<TreeNode>(list: any[], options?: Options) {
+export function buildTreeFromList<TreeNode>(list: any[], options?: Options): TreeNode[] {
   const { listFieldNames, treeFieldNames } = options || {}
   const { id: listIdField, parentId: listParentIdField } = { ...DEFAULT_FIELD_NAMES, ...listFieldNames }
   const { id: treeIdField, parentId: treeParentIdField, children: treeChildrenField } = { ...DEFAULT_FIELD_NAMES, ...treeFieldNames }
diff --git a/packages/tree/src/deepFirstTraverse.ts b/packages/tree/src/deepFirstTraverse.ts
index e93c45f..55bf215 100644
--- a/packages/tree/src/deepFirstTraverse.ts
+++ b/packages/tree/src/deepFirstTraverse.ts
@@ -40,7 +40,7 @@ interface TraverseAction<TreeNode> {
  * // output 'a', 'b', 'c'
  * ```
  */
-export function deepFirstTraverse<TreeNode>(tree: TreeNode | TreeNode[], action: TraverseAction<TreeNode>, options?: Options) {
+export function deepFirstTraverse<TreeNode>(tree: TreeNode | TreeNode[], action: TraverseAction<TreeNode>, options?: Options): void {
   if (!isFunction(action))
     throw new Error('traverse action should be a function')
 
diff --git a/packages/tree/src/flattenTree.ts b/packages/tree/src/flattenTree.ts
index 0408ae3..9fb3ef3 100644
--- a/packages/tree/src/flattenTree.ts
+++ b/packages/tree/src/flattenTree.ts
@@ -46,7 +46,7 @@ interface Options<TreeNode> {
     // ]
  * ```
  */
-export function flattenTree<TreeNode>(tree: TreeNode | TreeNode[], options?: Options<TreeNode>) {
+export function flattenTree<TreeNode>(tree: TreeNode | TreeNode[], options?: Options<TreeNode>): TreeNode[] {
   const { fieldNames, onEachTraverse } = options || {}
   const { children } = { ...DEFAULT_FIELD_NAMES, ...fieldNames }
 
diff --git a/packages/tree/src/treeFilterNode.ts b/packages/tree/src/treeFilterNode.ts
index 06ba55b..20d0c17 100644
--- a/packages/tree/src/treeFilterNode.ts
+++ b/packages/tree/src/treeFilterNode.ts
@@ -17,7 +17,7 @@ interface Options<TreeNode> {
  * @returns A filtered tree
  * @linkcode https://github.com/GreatAuk/utopia-utils/blob/main/packages/tree/src/treeFilterNode.ts
  */
-export function treeFilterNode<TreeNode>(tree: TreeNode[] | TreeNode, predicate: (node: TreeNode) => boolean, options?: Options<TreeNode>) {
+export function treeFilterNode<TreeNode>(tree: TreeNode[] | TreeNode, predicate: (node: TreeNode) => boolean, options?: Options<TreeNode>): TreeNode[] {
   const { fieldNames, onEachTraverse } = options || {}
   const { children } = { ...DEFAULT_FIELD_NAMES, ...fieldNames }
   const _tree = Array.isArray(tree) ? [...tree] : [tree]
diff --git a/packages/tree/src/treeFindNode.ts b/packages/tree/src/treeFindNode.ts
index 2147515..3019bcc 100644
--- a/packages/tree/src/treeFindNode.ts
+++ b/packages/tree/src/treeFindNode.ts
@@ -31,7 +31,7 @@ interface Options<TreeNode> {
     const res = treeFindNode(tree, node => node.name === 'b') // res is [{ name: 'b' }]
  * ```
  */
-export function treeFindNode<TreeNode>(tree: TreeNode[] | TreeNode, predicate: (node: TreeNode) => boolean, options?: Options<TreeNode>) {
+export function treeFindNode<TreeNode>(tree: TreeNode[] | TreeNode, predicate: (node: TreeNode) => boolean, options?: Options<TreeNode>): TreeNode[] {
   const { isFindAll, fieldNames, onEachTraverse } = options || {}
   if (!isFunction(predicate))
     throw new Error('predicate should be a function')
diff --git a/packages/tree/src/treeFindPath.ts b/packages/tree/src/treeFindPath.ts
index 6f0d6c9..ecd3566 100644
--- a/packages/tree/src/treeFindPath.ts
+++ b/packages/tree/src/treeFindPath.ts
@@ -31,7 +31,7 @@ interface Options {
     console.log(path?.map(v => v.name)) // ['a', 'b']
  * ```
  */
-export function treeFindPath<TreeNode>(tree: TreeNode[] | TreeNode, predicate: (node: TreeNode) => boolean, options?: Options) {
+export function treeFindPath<TreeNode>(tree: TreeNode[] | TreeNode, predicate: (node: TreeNode) => boolean, options?: Options): TreeNode[] | null {
   const { fieldNames } = options || {}
   const { children } = { ...DEFAULT_FIELD_NAMES, ...fieldNames }