eslint-plugin-no-typeof-window-undefined

ESLint rule that helps avoid typeof window === "undefined" check and fix it to typeof document === "undefined" instead. It's recommended to use document over window because server runtimes like Deno have a global window available.

Installation

pnpm add -D eslint eslint-plugin-no-typeof-window-undefined

Usage

Add to .eslintrc

{
  "extends": ["plugin:no-typeof-window-undefined/recommended"]
}

Rules

✅ Set in the recommended configuration

🔧 Automatically fixable by the --fix CLI option.

Name	Description	💼	🔧
no-typeof-window-undefined	Improve SSR/Browser environment check by using typeof document !== "undefined".	✅	🔧

no-typeof-window-undefined

Because the same JavaScript code can run in the browser as well as the server, sometimes you need to have a part of your code that only runs in one context or the other:

if (typeof window === "undefined") {
  // running in a server environment
} else {
  // running in a browser environment
}

This works fine in a Node.js environment, however, Deno actually supports window! So if you really want to check whether you're running in the browser, it's better to check for document instead:

if (typeof document === "undefined") {
  // running in a server environment
} else {
  // running in a browser environment
}

This will work for all JS environments (Node.js, Deno, Workers, etc.).

Credits

• https://twitter.com/JLarky/status/1598147116093693952
• Remix documentation