Best practices to avoid document is not defined error

Steps to Setup a NextJS App

To create a new Next.js application, follow these steps:...

When does this error occur?

The document object is part of the browser’s Window interface and represents the DOM (Document Object Model) of the current web page. When Next.js renders pages on the server, there is no browser environment, so the document object is not defined. This results in the “document is not defined” error when code that references the document is executed on the server....

Fixing Document not defined

Approach:...

Detailed Code Explanation

Using useEffect for Client-Side Execution: The useEffect hook in MyComponent ensures that the code accessing the document object only runs after the component mounts. This avoids server-side rendering issues, as document is not defined on the server.Accessing and Displaying Element Content: Inside the useEffect, document.getElementById(“some-id”) fetches the div element with id=”some-id”. If the element exists, its text content is retrieved and stored in the elementContent state. The content is then displayed inside an h2 tag, allowing dynamic updates based on the element’s content.Conditional Rendering: In the Home component, docEnv is set to true only if document is defined, ensuring that MyComponent is only rendered on the client side.’...

Best practices to avoid document is not defined error

Use useEffect to Run Client-Side Code: Ensure that code dependent on the document object is executed only on the client side by wrapping it in a useEffect hook.Check if document is Defined Before Accessing It: Perform a conditional check to confirm the existence of the document object.Use Dynamic Imports to Load Client-Side Components: Dynamically import components that rely on the document object to prevent them from being rendered on the server.Avoid Direct DOM Manipulation in SSR: Ensure that DOM manipulation code is only executed in the browser environment.Utilize Conditional Rendering: Render components or perform actions conditionally based on the environment to ensure code runs in the correct context....

Conclusion

“document is not defined” error in Next.js occurs because the document object is only available in the browser, not during server-side rendering. To avoid this error, use the useEffect hook to run client-side code, check if document is defined before accessing it, and use dynamic imports for client-side components. These practices ensure your application works seamlessly both on the server and in the browser....