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Events in JavaScript
Onmouseover Event in JavaScript
Bringing Websites to Life with Hover Effects
Exceptions of Onmouseover Event in JavaScript
Frequently Asked Questions
What are JavaScript events, and why are they important?
How do I attach an event to an HTML element?
Can I use onmouseover on mobile devices?
Last Updated: Mar 27, 2024

Onmouseover Event in JavaScript

Author Shiva
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Roadmap to SDE career at Amazon
Anubhav Sinha
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25 Jun, 2024 @ 01:30 PM


As you explore the internet, you may have come across websites that have responses to your actions. One interesting interaction you might have noticed is when an element on a webpage changes its appearance or behaviour when you hover your mouse over it. How does this happen? This can be done using Onmouseover Event in JavaScript. 

Onmouseover Event in JavaScript

In this article, we will take a look at Onmouseover Event in JavaScript and many more.

Events in JavaScript

Let's first take a moment to grasp JavaScript events before talking about the onmouseover event. Events on a web page are incidents or acts, as used in web development. These activities by the user, such as clicking a button, entering text into a text field, or hovering over an element, can start these events. Events operate as triggers to run JavaScript code, allowing programmers to create dynamic webpages.

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Onmouseover Event in JavaScript

Whenever the mouse cursor hovers over an element on a web page, JavaScript's onmouseover event is triggered. This component could be a button, picture, sentence, or whole section. Using this, developers can react to the mouse pointer entering this element's boundaries.

The syntax to attach the onmouseover event to an element looks like this:

element_name.onmouseover = function() {
     /* ... */

Let's break down this syntax:

  • element: This pertains to the HTML element you are focusing on. You are assigning an onmouseover event to this element. You can select the element using JavaScript methods such as getElementById, querySelector, or by referring to its HTML tag name
  • .onmouseover: This is the property that handles the event for the element. The code within it will run when the mouse pointer enters the boundaries of the element
  • function() { /* ... */ }: Here is where you write the JavaScript code that you want to execute when the onmouseover event happens

Bringing Websites to Life with Hover Effects

Now that we understand the basic concept of the onmouseover event. let's explore how it can create engaging hover effects on websites.

  • Changing Styles: Changing an element's style when a user hovers over it is one of the simplest and most popular uses of the onmouseover event. Changing attributes like the background colour, text colour, or font size may be necessary
  • Tooltips and Information: When a user hovers over particular items, hover effects can also display additional information or tooltips. This is especially helpful when you wish to give context for certain content
  • Interactive Animations: Taking hover effects a step further, you can use the onmouseover event to trigger interactive animations. Imagine you have a card on your website, and you want it to flip over when a user hovers over it. 

Exceptions of Onmouseover Event in JavaScript

There are specific situations where the onmouseover event won't function as expected. Let's take a look at these cases in simpler terms.

Instances When the Onmouseover Event Doesn't Work in JavaScript

There are specific situations where the onmouseover event won't function as expected. Let's take a look at these cases in simpler terms.

1. Certain HTML Tags: If we use the onmouseover event with certain HTML tags, it won't work as intended. These include tags like <html>, <script>, <style>, <title>, <head>, <meta>, <br>, <iframe>, <base>, <bdo>, and <param>

2. Missing Parentheses: When we write the HTML code, it's crucial to remember to use parentheses after the function name. For example:

onmouseover="function_name" -> incorrect

onmouseover="function_name()" -> correct

3. Undeclared Function: If the function used in the onmouseover event isn't declared in the JavaScript code, the event won't work as intended. Make sure to define the function properly in your JavaScript code for the event to function correctly


This example demonstrates a box that undergoes color and text transformations when it is hovered over. Upon hovering, the box transitions to an orange hue. Presents the text "Hovered!”, at its center. Once the mouse pointer is moved away, the box returns to its shade and displays the text "Hover Me."

You can experiment with this example by copying the code into an HTML file and opening it in a web browser. Hover over the box to see the onmouseover and onmouseout events in action, creating a basic hover effect.

  • HTML


<!DOCTYPE html>
<html lang="en">
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Onmouseover Event Example</title>
   .box {
       width: 100px;
       height: 100px;
       background-color: blue;
       color: white;
       text-align: center;
       line-height: 100px;
       cursor: pointer;
<div class="box" id="myBox">Hover Me</div>

const box = document.getElementById('myBox');

box.onmouseover = function() { = 'orange';
   box.textContent = 'Hovered!';

box.onmouseout = function() { = 'blue';
   box.textContent = 'Hover Me';




Frequently Asked Questions

What are JavaScript events, and why are they important?

Events in JavaScript act as signals, informing your code when anything occurs on a web page. By responding to user actions like clicking, typing, or moving the mouse, they make your website interactive. The ability to design dynamic and user-friendly web experiences makes events crucial.

How do I attach an event to an HTML element?

Using event attributes like onclick, onmouseover, or onkeydown directly in the HTML tag allows you to associate an event with an HTML element. As an alternative, you can choose the element using JavaScript and dynamically attach events using techniques like addEventListener.

Can I use onmouseover on mobile devices?

You can use a mouse on PCs and laptops, thus the answer is yes. However, since there is no mouse cursor on mobile devices like smartphones and tablets, things operate somewhat differently. Use touch-friendly events to make it operate correctly.


The onmouseover event in javascript is a flexible tool for building interactive online experiences, but developers should know its constraints and potential downsides. Developers may guarantee that hover effects improve the user experience without posing problems or aggravations by taking into account touch device compatibility, accessibility, performance, event bubbling, and usability.

Recommended Readings:

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