What is JavaScript? JavaScript (js) is a lightweight object-oriented programming language used by some websites to script web pages. It is an interpretable, full-fledged programming language that, when applied to HTML documents, enables dynamic interactivity on websites. It was introduced in 1995 to add programs to his web pages in the Netscape Navigator browser. It has since been adopted by all other graphical web browsers. Using JavaScript, you can create an up-to-date web application that users can interact with directly without having to refresh the page every time. Traditional websites use ‘js’ to provide many forms of interactivity and simplicity.
In this article, we will explore various essential topics in front-end development, focusing on HTML, CSS, and JavaScript, to equip you with the knowledge and skills needed to become a proficient front-end developer.
HTML
HTML (Hypertext Markup Language) is the standard markup language used for creating web pages. It consists of various tags that define the structure and content of a web page. Let's elaborate on some essential HTML tags with examples:
Headings
Headings are used to define the titles or headings of sections on a web page. HTML has six heading levels, from (most important) to (least important). An example is shown below.
<h1>Welcome to CipherSchools</h1>
<h2>Blogs</h2>
<h3>Our Articles</h3>
<!-- and so on... -->
Paragraphs
The <p> tag is used to define paragraphs of text on a web page:
<p>This paragraph specifies that you are reading an article by CipherSchools</p>
Lists
There are two types of lists in HTML: ordered lists and unordered lists.
Ordered List (<ol>): Represents a numbered list.
<ol>
<li>Blog/Article</li>
<li>CipherSchools</li>
</ol>
Unordered List (<ul>): Represents a bullet-pointed list.
<ul>
<li>Blog/Article</li>
<li>CipherSchools</li>
</ul>
Links
Links created using (anchor) tags take users to other websites or resources. The href attribute specifies the URL of the target.
<a href="">CipherSchools's Blog</a>
Image
The <img> tag can be used to display images on a web page. The image file's URL is specified by the src attribute:
<img src="image.jpg" alt="Description of the image">
There are few basic tags that are being used in HTML, there are certainly more such tags available to use. Check WhatsApp Clone using HTML and CSS for further details.
CSS Selectors:
Cascading Style Sheets (CSS) is a language used to control the appearance and layout of HTML documents. CSS selectors are a powerful tool that allows you to target and style specific HTML elements. Learn about different types of selectors, including element selectors, class selectors, and ID selectors, to give you precise control over the appearance of your web pages.
Types of CSS selectors –
· Element Selector - Select HTML elements directly by name.
· ID Selector - Selects the ID attribute of an element. IDs are always unique within your code. Therefore, they are used to target designs to specific or unique elements.
· Class Selector - Selects the class attribute of the element. Unlike ID selectors, class selectors can be the same for many elements.
· Universal Selector – Select all elements on a web page and apply changes to them.
· Group selection - used when the same style needs to be applied to many elements. Helps avoid code duplication.
JavaScript Basics (ES6)
JavaScript is a powerful and widely used programming language for web development. It allows developers to create dynamic and interactive web pages by manipulating the Document Object Model (DOM) and handling user interaction. JavaScript Fundamentals provides a foundation for building more complex applications and understanding advanced features of the language, especially those introduced in ES6 (ECMAScript 6).
1. Datatype
JavaScript has several data types, including:
Primitive Types: number, string, Boolean, null, undefined, and symbol.
Complex Types: object (arrays, functions, objects) and function.
let num = 10; // number
let str = 'Hello'; // string
let bool = true; // boolean
let arr = [1, 2, 3]; // Array
let obj = { name: 'CipherSchools', age: 25 }; // object
2. Variables:
In JavaScript, you can declare variables using the let, const, or var keywords.
let name = 'Cipher';
const PI = 3.14;
var age = 30; // Legacy way of declaring variables; avoid using in modern code.
3. Functions:
Functions are blocks of code that can be reused and called at any point in the program. ES6 introduced arrow functions, which provide a more concise syntax for defining functions.
// ES5 Function
function greet(name) {
return 'Cipher, ' + Schools;
}
// ES6 Arrow Function
const greet = (name) => `Hello, ${name}`;
4. Loops:
Loops allow you to execute a block of code repeatedly. Common loops in JavaScript are for and while loops.
// For loop
for (let i = 0; i < 5; i++) {
console.log(i); // Outputs: 0, 1, 2, 3, 4
}
// While loop
let count = 0;
while (count < 5) {
console.log(count); // Outputs: 0, 1, 2, 3, 4
count++;
}
5. Conditionals:
Conditionals allow you to make decisions in your code based on certain conditions. The common conditional statements are if, else if, and else.
const age = 18;
if (age < 18) {
console.log('You are a minor.');
} else if (age >= 18 && age < 65) {
console.log('You are an adult.');
} else {
console.log('You are a senior citizen.');
}
6. ES6 Features:
ES6 introduced many new features to extend the capabilities of JavaScript.
These features include, among others, the ability to:
1. Arrow function - A concise syntax for writing functions.
2. Class - A more structured, object-oriented way to define constructors and prototypes.
3. Module - You can organize your code in separate files and export/import functions.
4. Template literal - A simple way to manipulate strings using backticks ('').
5. Extension object literal - The short syntax for defining object properties and methods.
DOM (Document Model Object) Handling
The Document Object Model (DOM) is a programming interface provided by browsers that represent the structure of an HTML or XML document as a tree-like data structure. Each element in the document is represented as a node, and these nodes can be accessed, manipulated, and modified using JavaScript. Understanding DOM manipulation is crucial for creating dynamic, interactive, and responsive web applications.
1. Accessing DOM Elements:
There are numerous ways to access DOM elements in JavaScript. The most popular techniques are querySelector, getElementById, getElementsByClassName, and getElementsByTagName. These methods make it possible to obtain items from the DOM and alter their content and behavior.
// Accessing elements by ID
const header = document.getElementById('header');
// Accessing elements by class name
const buttons = document.getElementsByClassName('btn');
// Accessing elements by tag name
const paragraphs = document.getElementsByTagName('p');
// Accessing elements using CSS selector syntax
const firstListItem = document.querySelector('li');
2. Modifying DOM Elements:
Once you have access to a DOM element, you can change its content, attributes, and styles. For example, you can change the text content, update attributes such as src and href, and apply CSS styles to the element.
// Modifying text content
const element = document.getElementById('myElement');
element.textContent = 'Updated text';
// Updating attributes
const image = document.getElementById('myImage');
image.src = 'new_image.jpg';
// Applying CSS styles
const paragraph = document.getElementById('myParagraph');
paragraph.style.color = 'blue';
paragraph.style.fontSize = '16px';
3. Creating and Appending DOM Elements:
JavaScript can be also used to create new DOM elements and attach them to the document. This is useful for dynamically generating content on your page.
// Creating a new paragraph element
const newParagraph = document.createElement('p');
newParagraph.textContent = 'This is a dynamically created paragraph.';
// Appending the new paragraph to an existing element
const parentElement = document.getElementById('parent');
parentElement.appendChild(newParagraph);
4. Removing DOM Elements:
The removeChild method can be used to remove elements from the DOM. This is useful if you wish to delete existing parts and dynamically update the content.
const elementToRemove = document.getElementById('elementToRemove');
const parent = elementToRemove.parentNode;
parent.removeChild(elementToRemove);
5. Event Handling:
Event handling is an important part of DOM manipulation. You can attach event listeners to DOM elements to respond to user interactions such as clicks, key presses, and form submissions.
const button = document.getElementById('myButton');
button.addEventListener('click', () => {
alert('Button clicked!');
});
DOM (Document Object Model) Traversal
DOM (Document Object Model) processing is a fundamental aspect of front-end web development because it allows you to dynamically interact and manipulate HTML and XML documents on your web pages. DOM manipulation is essential for creating interactive user interfaces, updating content, and responding to user actions. It introduces some important concepts and techniques related to DOM processing.
Event Handling:
Event handling is an important part of DOM manipulation. You can attach event listeners to DOM elements to respond to user interactions such as clicks, key presses, and form submissions
// Accessing elements by ID
const elementById = document.getElementById('elementId');
// Accessing elements by class name
const elementsByClass = document.getElementsByClassName('className');
// Accessing elements by tag name
const elementsByTag = document.getElementsByTagName('tagName');
// Accessing elements using CSS selector syntax
const elementBySelector = document.querySelector('cssSelector');
const elementsBySelectorAll = document.querySelectorAll('cssSelector');
2. Modifying DOM Elements:
Once you have access to a DOM element, you can change its content, attributes, and styles to dynamically update your web page.
// Modifying text content
elementById.textContent = 'New text content';
// Updating attributes
elementById.src = 'new_image.jpg';
// Applying CSS styles
elementById.style.color = 'blue';
elementById.style.fontSize = '16px';
3. Creating and Appending DOM Elements:
You can use JavaScript to dynamically create new DOM elements and append them to existing documents.
// Creating a new element
const newElement = document.createElement('p');
newElement.textContent = 'This is a dynamically created paragraph.';
// Appending the new element to an existing element
const parentElement = document.getElementById('parent');
parentElement.appendChild(newElement);
4. Removing DOM Elements:
DOM elements can be removed from the document using the removeChild method. This is useful for dynamically updating content or removing existing items.
const elementToRemove = document.getElementById('elementToRemove');
const parent = elementToRemove.parentNode;
parent.removeChild(elementToRemove);
5. Event Handling:
Event handling is an important part of DOM manipulation. You can attach event listeners to DOM elements to respond to user interactions such as clicks, key presses, and form submissions.
const button = document.getElementById('myButton');
button.addEventListener('click', () => {
alert('Button clicked!');
});
6. Traversing the DOM:
DOM traversal allows you to navigate the tree-like structure of your document to find specific elements or their relationships. You can switch between parent, child, and sibling elements.
const parentElement = document.getElementById('parent');
const firstChildElement = parentElement.firstChild;
const nextSiblingElement = firstChildElement.nextSibling;
const previousSiblingElement = nextSiblingElement.previousSibling;
Working with the DOM is a must-have skill for front-end developers. This allows you to create dynamic, interactive web applications that respond to user actions and update content in real time. Knowing how to access, modify, and manipulate the DOM allows you to create seamless, user-friendly web experiences. Practice and experiment with DOM manipulation to become proficient and improve your web development skills.
Events
Events play an important role in web development as they allow web applications to react to user actions and various browser-related events.
Understanding and handling events is essential to creating interactive and dynamic web pages that provide a seamless user experience. In JavaScript, you can attach event listeners to her HTML elements to respond to specific events and execute appropriate JavaScript code.
1. Attaching Event Listeners:
To respond to events, attach event listeners to specific HTML elements. An event listener is a function that "listens" for the occurrence of a particular event, and when that event is triggered, the associated function is executed.
const button = document.getElementById('myButton');
button.addEventListener('click', () => {
// Code to be executed when the button is clicked
});
2. Common Events:
There are many events that can be manipulated, depending on the user interaction and browser-related events you want to handle. Here are some common events:
Mouse Events:
· click: Triggered when the element is clicked.
· mouseover/mouseout: Triggered when the mouse pointer enters/leaves the element.
· mousemove: Triggered when the mouse pointer moves over the element.
Keyboard Events:
· keydown: Triggered when a key is pressed.
· keyup: Triggered when a key is released.
· keypress: Triggered when a key is pressed and held down.
Form Events:
· submit: Triggered when a form is submitted.
· reset: Triggered when a form is reset.
Focus Events:
· focus: Triggered when an element receives focus.
· blur: Triggered when an element loses focus.
Window Events:
· load: Triggered when the page finishes loading.
· resize: Triggered when the window is resized.
· scroll: Triggered when the user scrolls the page.
3. Event Handling:
Event handling involves writing code to respond to specific events and perform actions accordingly. For example, you can change the text of an element when a button is clicked or display an alert when the user submits a form.
Object-Oriented JavaScript
Object-oriented programming (OOP) is a programming paradigm focused on creating objects with properties and behavior, encapsulating data, and functionality in a single entity. JavaScript lets you explore the concepts of classes, objects, inheritance, and prototyping to organize and structure your code more effectively.
For a detailed explanation do check – Introduction to Object Oriented Programming