JavaScript Roadmap

[rajatranjanrai]

Detailed Description

Give Full Details of Events Listner and DOM BOM

[Ay-2510]

Event Listener:

An Event Listener is a programming construct in web development that enables developers to attach an event handler to a specific element on a web page. It listens for events triggered by user interactions (such as clicks, mouse movements, keyboard inputs, etc.) or by the browser itself (such as page loading, resizing, etc.). When the specified event occurs, the associated event handler function is executed.

Here's how Event Listeners work in JavaScript:

Attaching Event Listeners: Developers can attach event listeners to HTML elements using JavaScript. This is typically done by selecting the desired HTML element using methods like getElementById, querySelector, or getElementsByClassName, and then calling the addEventListener method on the selected element.

example:

const button = document.getElementById('myButton');
button.addEventListener('click', function() {
    // Event handler function
    console.log('Button clicked!');
});

Types of Events: There are various types of events that can be listened for, such as 'click', 'mouseover', 'keydown', 'submit', 'load', etc. The choice of event depends on the desired interaction to be captured.

Event Handler Function: The second argument to addEventListener is a function that gets executed when the specified event occurs. This function can contain any JavaScript code that needs to run in response to the event.

Removing Event Listeners: Event listeners can also be removed using the removeEventListener method. example: button.removeEventListener('click', myEventHandler);

DOM (Document Object Model):

The DOM is a programming interface for web documents. It represents the structure of an HTML or XML document as a tree-like structure wherein each node represents a part of the document, such as elements, attributes, and text. JavaScript can manipulate the DOM dynamically, enabling developers to add, remove, or modify elements and content on a web page after it has loaded.

BOM (Browser Object Model):

The BOM represents everything in the web browser outside of the actual web page content. It includes objects such as window, navigator, screen, history, and location. The window object is the top-level object in the BOM hierarchy and represents the browser window. It provides methods and properties for controlling the browser, such as opening new windows, setting timeouts, and navigating to different URLs.