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Ev Onfocus
Ev Onfocus
📅 2026-06-18 | 📂 HTML
# HTML onfocus Event Attribute The `onfocus` event attribute fires the moment an element receives focus. This is most commonly used on form fields (like `
`, `
`), hyperlinks (`
`), and other interactive elements to trigger a JavaScript function when a user clicks on or tabs to the element. --- ## Browser Support The `onfocus` attribute is universally supported across all major modern browsers: * Google Chrome * Mozilla Firefox * Microsoft Edge / Internet Explorer * Safari * Opera --- ## Definition and Usage The `onfocus` attribute is an event listener that executes a script when an element becomes the active element in the document. ### Key Characteristics: * **Common Targets:** It is most frequently used with `
`, `
`, `
`, and `<a>` elements. * **Opposite Event:** The opposite of the `onfocus` event is the [`onblur`](ev-onblur.html) event, which fires when an element loses focus. * **Non-focusable Elements:** The `onfocus` attribute cannot be used on the following elements: `<base>`, `<bdo>`, `<br>`, `<head>`, `<html>`, `<iframe>`, `<meta>`, `<param>`, ` </head> <body> <p>Click inside the input field to trigger the onfocus event:</p> <input type="text" id="fname" onfocus="setStyle(this.id)"> <!-- Global Analytics Tracker --> <script> // Placeholder for Google Analytics </script> </body> </html> ``` ### Example 2: Modern JavaScript Event Listener (Recommended) While inline HTML attributes are quick to write, separating your JavaScript from your HTML structure is a best practice. You can achieve the same result using `addEventListener`: ```html <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>onfocus Event Listener Example</title> </head> <body> <p>Click inside the input field to trigger the focus event:</p> <input type="text" id="username"> <!-- Global Analytics Tracker --> <script> // Placeholder for Google Analytics </script> </body> </html> ``` --- ## Considerations and Best Practices 1. **Accessibility (a11y):** Ensure that any visual changes triggered by `onfocus` are also accessible to screen readers and keyboard-only users. Do not rely solely on color changes to convey important information. 2. **Focus Bubbling:** In standard JavaScript, the `focus` event **does not bubble** up the DOM tree. If you need to capture focus events on a parent element (event delegation), you should use the `focusin` event instead. 3. **Avoid Infinite Loops:** Be careful when using `alert()` or modifying focus programmatically inside an `onfocus` handler, as it can easily cause an infinite loop of focus events that freezes the browser.</div><div class="post-nav"><a href="/post/ev-onselect.html">← Ev Onselect</a><a href="/post/ev-onchange.html">Ev Onchange →</a></div></div> <div class="sidebar"><div class="sidebar-widget"><h3>📂 Categories</h3><ul><li><a href="/category/18.html">⚡ JavaScript</a> <span style="color:#999;font-size:12px">(1589)</span></li><li><a href="/category/23.html">🐘 PHP</a> <span style="color:#999;font-size:12px">(872)</span></li><li><a href="/category/27.html">🐍 Python3</a> <span style="color:#999;font-size:12px">(810)</span></li><li><a href="/category/15.html">🌐 HTML</a> <span style="color:#999;font-size:12px">(691)</span></li><li><a href="/category/31.html">⚙️ C#</a> <span 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