What is an Event Listener in JavaScript? An In-Depth Guide
Table of Content:
An event listener is a function in JavaScript that is attached to an event on an element in a webpage. When the event is triggered, the listener function is executed. This allows you to specify the actions that should be taken when a particular event occurs on an element, such as a button click or a form submission.
For example, you can use an event listener to execute a function when a button is clicked:
<span class="pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class="pun">(</span><span class="str">"myButton"</span><span class="pun">).</span><span class="pln">addEventListener</span><span class="pun">(</span><span class="str">"click"</span><span class="pun">,</span><span class="pln"> myFunction</span><span class="pun">);</span>
In this example, the function myFunction is attached as an event listener to the "click" event on the button with the ID "myButton". When the button is clicked, the function will be executed.
Event listeners are a powerful tool for creating interactive and dynamic webpages. They can be attached to a wide range of events on different elements, such as mouse clicks, keyboard input, form submissions, and more.
Example of Click event Listener in javascript
Here is an example of using an event listener to execute a function when a button is clicked in JavaScript:
<span class="pln"> </span><span class="tag"><button</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"myButton"</span><span class="tag">></span><span class="pln">Click me!</span><span class="tag"></button></span><span class="pln"> </span><span class="tag"><script></span><span class="pln"> </span><span class="com">// Define the function to be executed when the button is clicked</span><span class="pln"> </span><span class="kwd">function</span><span class="pln"> buttonClicked</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln"> alert</span><span class="pun">(</span><span class="str">"Button was clicked!"</span><span class="pun">);</span><span class="pln"> </span><span class="pun">}</span><span class="pln"> </span><span class="com">// Attach the function as an event listener to the "click" event on the button</span><span class="pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class="pun">(</span><span class="str">"myButton"</span><span class="pun">).</span><span class="pln">addEventListener</span><span class="pun">(</span><span class="str">"click"</span><span class="pun">,</span><span class="pln"> buttonClicked</span><span class="pun">);</span><span class="pln"> </span><span class="tag"></script></span><span class="pln"> </span>
In this example, the function buttonClicked is defined and is attached as an event listener to the "click" event on the button with the ID "myButton". When the button is clicked, the function will be executed and an alert message will be displayed.
Event listeners can be attached to any element in a webpage, and they can be triggered by a wide range of events, such as mouse clicks, keyboard input, form submissions, and more.
Full Code. You can copy it and use it.
<span class="pln"> </span><span class="dec"><!DOCTYPE html></span><span class="pln"> </span><span class="tag"><html></span><span class="pln"> </span><span class="tag"><body></span><span class="pln"> </span><span class="tag"><h2></span><span class="pln">Example of Click event Listener in javascript</span><span class="tag"></h2></span><span class="pln"> </span><span class="tag"><button</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"myButton"</span><span class="tag">></span><span class="pln">Click me!</span><span class="tag"></button></span><span class="pln"> </span><span class="tag"></body></span><span class="pln"> </span><span class="tag"></html></span><span class="pln"> </span><span class="tag"><script></span><span class="pln"> </span><span class="com">// Define the function to be executed when the button is clicked</span><span class="pln"> </span><span class="kwd">function</span><span class="pln"> buttonClicked</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln"> alert</span><span class="pun">(</span><span class="str">"Button was clicked!"</span><span class="pun">);</span><span class="pln"> </span><span class="pun">}</span><span class="pln"> </span><span class="com">// Attach the function as an event listener to the "click" event on the button</span><span class="pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class="pun">(</span><span class="str">"myButton"</span><span class="pun">).</span><span class="pln">addEventListener</span><span class="pun">(</span><span class="str">"click"</span><span class="pun">,</span><span class="pln"> buttonClicked</span><span class="pun">);</span><span class="pln"> </span><span class="tag"></script></span><span class="pln"> </span>