Solving the TypeError: Clipboard.on is not a function in JavaScript Testing

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In this post, we’ll walk you through the cause of this error and how to solve it.

Understanding the Problem

The Error

In your testing environment, when trying to execute functionality from the Clipboard class, you encounter the following error message:

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

Context of the Issue

The Solution

Adding the on Method

To resolve this issue, you need to ensure that the Clipboard class has an on method defined. Adding a dummy implementation of this method can resolve the testing issue by simulating the behavior you expect during the test.

Improved Clipboard Class

Here's how you can adjust your Clipboard class to include the on method:

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

Explanation of the Code

Clipboard Class: The class serves as a mock for your clipboard functionality.

Constructor: The constructor captures the arguments passed to it, allowing you to potentially extend functionality later if needed.

on Method: This method accepts two parameters. The first (success) is a placeholder (we're not using it for testing). The second, show_copied_confirmation, is the function that gets called when clipboard interactions succeed. In this case, it gets executed immediately, simulating the success response expected during your test.

Update Your Test Configuration

Once you've added the on method, your test setup should no longer throw the TypeError. Run your tests again to ensure everything functions as expected.

Additional Considerations

Functionality Testing: Since this solution adds a mocked functionality, ensure that your actual implementation (when working outside of test scenarios) correctly handles clipboard interactions.

Mock Libraries: If you’re working on larger projects, consider utilizing mocking libraries which can simulate complex behaviors without writing everything manually.

Conclusion

Remember, effective testing practices are key to ensuring long-term success in your JavaScript projects. With the right approach, you can easily handle unexpected errors and create a more reliable codebase. Happy coding!