Скачать или смотреть How to Edit span Content with an onclick Button Function in JavaScript

Learn how to successfully edit span content in a JavaScript application using the `onclick` function, solving common errors and implementing best practices.
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This video is based on the question https://stackoverflow.com/q/64787451/ asked by the user 'Emil Avara' ( https://stackoverflow.com/u/7535634/ ) and on the answer https://stackoverflow.com/a/64787618/ provided by the user 'mplungjan' ( https://stackoverflow.com/u/295783/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Building a To-Do Application in JavaScript: Editing To-Do Items

Creating a To-Do application is a fantastic way to practice your JavaScript skills. In this guide, we'll tackle a common issue faced by developers: how to edit the content of span elements with an onclick function. If you've encountered the frustrating "span is null" error, then this guide is tailored for you.

Understanding the Problem

You may want users to have the ability to edit their To-Do items directly in the list. When trying to implement this functionality with an onclick event, you might get the error indicating the span is null. This is usually due to a misunderstanding of how to correctly navigate the DOM to access the span that contains the text.

The Initial Code

Firstly, let’s look at the original code structure for adding a new item, along with the editToDo function that triggered the error:

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

Issues in the Original Code

Incorrect Span Selection: The line var span = button.closest('span'); does not correctly find the span element because closest looks for a parent matching the selector, not a sibling.

Using appendChild with a String: The method span.appendChild(edit); attempts to append a string (the edited text) to a text node, which is not allowed.

How to Fix It

Step-by-Step Solution

Select the Correct Span: Use closest('li') to first locate the li containing the button. From there, use querySelector('span') to target the span specifically.

Update Content Directly: Instead of using appendChild, which is intended for Node objects, update the textContent of the span directly with the new value.

Here’s the corrected editToDo function:

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

Complete JavaScript Code Example

Below is a complete refactored version of your JavaScript functions, integrating the changes:

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

Enhancing the User Experience

To take your To-Do application a step further, consider refactoring your code to utilize event delegation, making it more efficient:

Using Event Delegation: Instead of setting individual event listeners on each button after creation, attach one listener to the parent element and handle all button clicks in one go.

Final JavaScript Example with Delegation

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

Conclusion

Incorporating these changes will resolve the "span is null" error and greatly enhance the editing functionality within your To-Do application. Practice integrating these concepts into your project, and you'll soon be on your way to building more responsive and user-friendly applications.

Don't hesitate to experiment and make further refinements, such as adding styling for buttons or creating a more advanced user interface!