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Troubleshooting document is not defined Error in React Native and React Native Web

Updated by Tim Rabbetts on

When developing applications with React Native and trying to extend them to the web using React Native Web, developers might encounter the 'document is not defined' error. This article aims to explain the root cause of this issue and provide solutions to resolve it.

In JavaScript, 'document' is a global object in browsers that represents the HTML document loaded in that browser window. It is part of the DOM (Document Object Model) and is used extensively in web development to manipulate HTML and CSS dynamically.

React Native, however, does not use the browser's DOM as it targets mobile platforms. Instead, it manipulates the native views of the platform. When React Native code that references the 'document' object is executed in a mobile environment or when using React Native Web, it results in the 'document is not defined' error because the 'document' object is undefined in non-browser environments.

This error typically occurs under several scenarios:

  • Using browser-specific APIs like 'document' or 'window' directly in your React Native code.
  • Importing a library or module that relies on browser-specific objects in a React Native environment.
  • Incorrectly configuring or setting up React Native Web which leads to environmental discrepancies.

The following strategies can help fix or avoid the 'document is not defined' error:

  • Conditional Use: Before using browser-specific objects, check if they exist. For example: 
    
          if (typeof document !== 'undefined') {
            // safe to use the document object
            document.title = 'New Title';
          }
  • Server-Side Rendering (SSR) Checks: Ensure that the code intended for the web does not run in the server-side rendering process or in a non-web environment.
  • Platform-Specific Code: Utilize the 'Platform' module from React Native to run certain code only on specific platforms. For example: 
    
          import { Platform } from 'react-native';
          if (Platform.OS === 'web') {
            // run web specific code
          }
  • Universal Libraries: Opt for libraries that support both web and mobile platforms or handle the environment-specific functionalities internally.
  • Proper Configuration: Properly configure React Native Web in your project to avoid cross-environment issues.

By understanding the environments in which your React Native application runs, and by taking careful steps to handle cross-environment functionality, the 'document is not defined' error can be effectively managed and resolved. Adapt your development practices to accommodate both mobile and web platforms, ensuring a smooth development process.

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