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Vue.js: "TypeError: is not a function"

Introduction: Vue.js is a popular JavaScript framework for building user interfaces and single-page applications. While working with Vue.js, developers may encounter various errors that can hinder their progress. One such error is the "TypeError: is not a function" error. In this article, we will delve into the root cause of this error and provide a solution to fix it.

Understanding the Error: The error message "TypeError: is not a function" typically arises when using the Vue Router in conjunction with an outdated version of the Vue Devtools Chrome extension. It indicates that the 'now' function, which is a part of the Vue Router API, is not recognized as a valid function.

Explanation: The Vue Router is a crucial component in Vue.js applications as it enables navigation between different views or components within the application. The Vue Devtools Chrome extension, on the other hand, provides developers with powerful tools for inspecting, debugging, and profiling Vue.js applications.

However, due to the evolution of Vue.js and its related ecosystem, compatibility issues may arise between different versions of Vue Router and the Vue Devtools extension. In this case, an older version of the Vue Devtools Chrome extension might not be compatible with the Vue Router's 'now' function, leading to the "TypeError: is not a function" error.

Solution: To resolve this error, follow these steps:

  1. Check the version of the Vue Devtools Chrome extension installed on your browser. You can do this by navigating to the Chrome Extensions page (chrome://extensions) and locating the Vue Devtools extension.

  2. If you find that you have an older version installed, it is highly recommended to update it to the latest version available. You can do this by visiting the Chrome Web Store ( and searching for "Vue Devtools."

  3. Once you find the Vue Devtools extension, click on the "Update" button if it's available. Alternatively, you can uninstall the existing version and install the latest version from scratch.

  4. After updating or reinstalling the Vue Devtools extension, restart your browser to ensure the changes take effect.

  5. Finally, revisit your Vue.js application and check if the "TypeError: is not a function" error has been resolved. In most cases, updating the Vue Devtools extension should fix the compatibility issue and allow the 'now' function to be recognized properly.

Conclusion: The "TypeError: is not a function" error in Vue.js is typically encountered when using an older version of the Vue Devtools Chrome extension in conjunction with the Vue Router. By updating the Vue Devtools extension to the latest version, you can resolve this error and continue developing your Vue.js application without any hindrance. Remember to keep your development tools up to date to leverage the full potential of the Vue.js ecosystem and its related libraries.



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