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JAVASCRIPT
<title>Event Handling Example</title>
<button id="myButton">Click Me</button>
<div id="myDiv">Hover over me</div>
// Selecting the elements
const button = document.getElementById('myButton');
const div = document.getElementById('myDiv');
// Click event handler
function handleClick(event) {
console.log('Button was clicked!');
// Add your code here to perform actions when the button is clicked.
}
// Hover event handler
function handleHover(event) {
console.log('Mouse is over the div!');
// Add your code here to perform actions when the mouse hovers over the div.
}
// Attaching the event listeners
button.addEventListener('click', handleClick);
div.addEventListener('mouseover', handleHover);
In this example, we have a button and a div element, and we attach event listeners to them to handle the click and hover events, respectively. When you click the button, the handleClick function will be executed, and when you hover over the div, the handleHover function will run.
Remember to always include your JavaScript code after the DOM elements have been loaded (either by placing the script at the bottom of the body or using the DOMContentLoaded event) to ensure that the elements are accessible when attaching the event listeners.
const bodyElement = document.body; // Accessing the body element of the document
const titleElement = document.getElementById('title'); // Accessing an element with id="title"
Element: The
Elementobject represents an individual HTML element within the DOM. In other words, any HTML tag, such as<div>,<p>,<a>, etc., corresponds to anElementobject when parsed into the DOM tree.
Key Characteristics:
The
Elementinterface extends theNodeinterface (hence, it has all the properties and methods of theNode).It provides access to properties and methods specific to HTML elements, such as
innerHTML,classList,style, etc.Elements can be selected using methods like
getElementById,querySelector, or by accessing properties likedocument.body, etc.
Example:
<div id="myDiv">This is a div element</div>
const myDivElement = document.getElementById('myDiv'); // Accessing the div element
Node: The
Nodeobject represents a single node in the DOM tree. A node can be an element node, a text node, an attribute node, or any other type of node defined in the DOM. Both theDocumentandElementobjects are subclasses of theNodeobject, meaning they inherit its properties and methods.
Key Characteristics:
The
Nodeinterface provides basic properties and methods for all types of nodes, such asnodeType,nodeName,nodeValue,appendChild,removeChild, etc.Nodes can be elements, text, comments, document type declarations, etc.
Example:
<p>This is a <em>paragraph</em> element</p>
const paragraphNode = document.querySelector('p'); // Accessing the paragraph element node
const textNode = paragraphNode.firstChild; // Accessing the text node containing "This is a "
const emphasisNode = paragraphNode.querySelector('em'); // Accessing the em (emphasis) element node
In summary, the Document represents the entire HTML document, the Element represents individual HTML elements, and the Node is the basic unit that forms the DOM tree, including elements and other types of nodes. Elements are nodes, but not all nodes are elements.
<title>Accessing Element Attributes</title>
<img id="myImage" src="image.jpg" alt="A beautiful image">
<a id="myLink" href="https://www.example.com" target="_blank">Visit Example</a>
// Accessing attributes using getAttribute()
const imageElement = document.getElementById('myImage');
const linkElement = document.getElementById('myLink');
const imageSrc = imageElement.getAttribute('src');
const linkHref = linkElement.getAttribute('href');
console.log(`Image source: ${imageSrc}`);
console.log(`Link href: ${linkHref}`);
Directly accessing element properties:
Some attributes have corresponding properties that can be accessed directly from the element object. For example, the src attribute of an <img> tag has a corresponding src property.
<title>Accessing Element Properties</title>
<img id="myImage" src="image.jpg" alt="A beautiful image">
<a id="myLink" href="https://www.example.com" target="_blank">Visit Example</a>
// Accessing attributes using element properties
const imageElement = document.getElementById('myImage');
const linkElement = document.getElementById('myLink');
const imageSrc = imageElement.src;
const linkHref = linkElement.href;
console.log(`Image source: ${imageSrc}`);
console.log(`Link href: ${linkHref}`);
Note that not all attributes have corresponding properties. In such cases, you should use the getAttribute() method to access the attribute values.
Using either method, you can read the values of attributes associated with an element in the DOM, which allows you to retrieve important information from HTML elements, such as image sources, links, data attributes, and more.
<title>Setting Styles with JavaScript</title>
/* Define a CSS class */
.highlight {
background-color: yellow;
color: black;
font-weight: bold;
}
<p id="myParagraph">This is a paragraph.</p>
<button id="myButton">Click Me</button>
// Select the elements
const paragraphElement = document.getElementById('myParagraph');
const buttonElement = document.getElementById('myButton');
// Set styles using the style property
paragraphElement.style.backgroundColor = 'blue';
paragraphElement.style.color = 'white';
paragraphElement.style.fontSize = '18px';
// You can also set styles using a CSS class
buttonElement.classList.add('highlight');
In the example above, we have a paragraph element and a button. We use JavaScript to set the styles for the paragraph and apply a CSS class to the button element.
To set styles using the style property:
Access the element you want to style using methods like
getElementById,querySelector, etc.Use the
styleproperty of the element to access its CSS properties.Set the desired CSS properties as if you were modifying the inline style attribute of the element in HTML.
To set styles using a CSS class:
Define a CSS class with the desired styles in a
<style>tag or external stylesheet.Use JavaScript to add the class to the
classListproperty of the element you want to style. TheclassList.add()method adds the specified class to the element.
By using JavaScript to set styles, you can dynamically change the appearance of elements on your web page based on various conditions or user interactions.
<title>Dynamic Element Creation and Styling</title>
<button id="createButton">Create Box</button>
<div id="container"></div>
const createButton = document.getElementById('createButton');
const container = document.getElementById('container');
createButton.addEventListener('click', () => {
// Create a new div element
const newBox = document.createElement('div');
// Set styles for the new div element
newBox.style.width = '100px';
newBox.style.height = '100px';
newBox.style.backgroundColor = 'red';
newBox.style.margin = '10px';
// Add the new element to the container
container.appendChild(newBox);
});
In this example, clicking the “Create Box” button will create a new <div> element with specified styles (width, height, background color, and margin) and add it to the container div.
Modifying Existing Element Styles:
To modify styles of existing elements:
<title>Modifying Element Styles</title>
<div id="myDiv">This is a div element.</div>
const myDiv = document.getElementById('myDiv');
// Modifying the existing styles
myDiv.style.backgroundColor = 'blue';
myDiv.style.color = 'white';
myDiv.style.fontSize = '18px';
In this example, the JavaScript code modifies the background color, text color, and font size of the existing <div> element with the id “myDiv”.
By using the style property, you can directly access and modify the inline styles of elements. However, it’s worth noting that inline styles can be overwritten by other styles defined in CSS, so using classes and CSS rules is often a better practice for more complex styling scenarios.
To apply multiple styles to an element, you can also use CSS classes. Here’s how you can add a class to an element dynamically:
const element = document.getElementById('myElement');
element.classList.add('myClass');
With this approach, you define the styles in a CSS class and toggle the class on or off for elements as needed. This allows you to manage styles more efficiently and separate them from your JavaScript code.
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