How to Fix ReferenceError: document is not defined in NextJS When Accessing Cookies

Learn how to resolve the common `ReferenceError: document is not defined` error in NextJS when accessing cookies in this step-by-step guide.
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How to Fix ReferenceError: document is not defined in NextJS When Accessing Cookies

If you're developing a NextJS application and trying to access cookies, you might encounter a ReferenceError: document is not defined error. This error typically occurs because NextJS leverages both server-side and client-side rendering, and the document object is not available on the server side.

Understanding the Error

How to Fix It

To resolve this error, you need to ensure that any code attempting to access the document object only runs on the client side. There are a few methods to achieve this:

Conditional Checking

You can use conditional checks to ensure that the code accessing the document object only runs on the client side. For example:

[[See Video to Reveal this Text or Code Snippet]]

Using useEffect Hook in Functional Components

For functional components, you can use the useEffect hook which runs only after the component has mounted (client-side):

[[See Video to Reveal this Text or Code Snippet]]

Component Lifecycle Methods in Class Components

If you are using class components, you can safely access the document object in lifecycle methods that run after the component has mounted, such as componentDidMount:

[[See Video to Reveal this Text or Code Snippet]]

Summary

Encountering a ReferenceError: document is not defined in NextJS when accessing cookies is a common issue due to the nature of server-side rendering. The solutions require you to ensure that any access to the document object is confined to the client side, using techniques like conditional checks, the useEffect hook, or component lifecycle methods.

By implementing these practices, you can safely handle cookies without running into the ReferenceError, ensuring a smoother development experience with NextJS.