Solving the JavaScript Event Listener Issue in Login Forms

Learn how to fix the issue where a JavaScript event listener fires before the form is submitted in your HTML login forms.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Event listener function executed when page is loaded but event not happening

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Troubleshooting JavaScript Event Listener Issues in Login Forms

As a beginner in web development, you might encounter situations that seem illogical at first, especially when working with JavaScript and event listeners. One common problem is when the function assigned to an event listener is executed immediately, rather than waiting for the event to occur. This is particularly true for those setting up a login form in HTML using JavaScript. Today, we’ll explore why this happens and how to resolve it effectively.

The Issue: Immediate Function Execution

In your code, you set up an event listener for a button click to handle the login process. However, you noticed that the event listener callback function runs right when the page loads, instead of when the button is clicked. This is confusing and prevents the login form from functioning as expected.

Here’s a brief recap of the relevant part of your JavaScript code:

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

In this line, the login() function is invoked immediately instead of being provided as a function reference to be called when the button is clicked.

The Solution: Using Function Reference Instead of Function Call

To ensure the event listener only runs the function when the button is clicked, you must pass the function reference rather than invoking it. This can be corrected with the following change:

Updated JavaScript Code

Replace the existing event listener line in the login_handler() function with this:

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

By using just login, you’re passing the function as a reference without executing it immediately.

Full JavaScript Outline

Here’s how your corrected JavaScript function might look:

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

Conclusion

By making this simple adjustment, your login form should now work correctly: the login() function will execute only when the user clicks the "Login" button, not when the page loads. This is a small but critical insight into JavaScript event handling and can significantly enhance your web development skills as you continue to learn.

If you have any more questions about JavaScript or web development, don’t hesitate to ask. Happy coding!