Why is TypeError: is not a function in WordPress?

The error “TypeError: is not a function” in WordPress typically occurs when you’re trying to call a function that doesn’t exist or isn’t recognized by JavaScript or PHP, which are the two main scripting languages used in WordPress.

Here are the possible reasons:

  1. Script Loading Order: If you’re working with JavaScript and your script is trying to call a function before it has been loaded or defined, you will see this error. This can happen if your scripts are not loaded in the right order.

  2. Out of Scope: A function may not be available if it is defined within a certain scope and you are trying to call it from outside of that scope.

  3. Plugin or Theme Conflict: Sometimes, a plugin or theme may cause this error. This can happen if a plugin or theme incorrectly declares a function or interferes with the loading of scripts.

  4. Typographical Errors: A simple typographical error in the function name can also trigger this error. Even the slightest spelling mistake or case sensitivity error can lead to this problem.

To troubleshoot the error, you can follow these steps:

  • Check the function that is causing the error. Verify if the function is spelled correctly and respects case sensitivity.
  • Ensure your scripts are loaded in the correct order. Dependencies should be loaded before the scripts that use them.
  • If you’re working with JavaScript, make sure that the function is in the right scope.
  • Try deactivating your plugins one by one and switch to a default WordPress theme to see if the error persists. If the error disappears after deactivating a specific plugin or changing the theme, then you’ve found the culprit.

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