Course Content
Introduction to JavaScript
JavaScript is one of the most popular and widely used programming languages in the world. It plays a crucial role in web development, enabling dynamic content, interactivity, and enhanced user experiences in web pages and applications. Let’s dive into what JavaScript is, its history, and how it fits into the modern web.
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How to Add JavaScript?
Before diving into the basics of JavaScript, it’s essential to understand how to include JavaScript in an HTML file. There are three main ways to do this:
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Different Ways to Output Data
JavaScript provides several ways to "display" or output data, allowing you to present dynamic content to users in various ways. Each method serves a different purpose and is used in different scenarios depending on the requirements. Here are the primary methods for displaying data using JavaScript:
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Variables and Constants
Variables and constants in JavaScript are used to store data values. Depending on how you declare them, their value can be changed or fixed.
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Data Types
JavaScript provides different types of values that can be stored in variables. These are categorized into two types: Primitives and Non-Primitives.
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Conditional Statements (if, else if, else)
Conditional statements execute different actions based on different conditions.
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Arrays
In JavaScript, an array is a special type of object that stores an ordered collection of values (elements). Arrays are zero-indexed, meaning the first element is accessed with index 0.
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DOM Manipulation
DOM Manipulation is the process of using JavaScript to interact with and modify the HTML and CSS of a webpage. The DOM is essentially the structure of the webpage, represented as nodes, which can be elements, attributes, or pieces of text.
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String Functions in JavaScript
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Number Functions in Javascript
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RegEx (Regular Expressions) in JavaScript
Regular expressions (regex) are patterns used to match sequences of characters in strings. They are powerful tools for searching, validating, and manipulating text.
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JavaScript
About Lesson

To interact with elements in the DOM, you first need to select them. JavaScript provides a range of methods to target specific elements.

This method selects an element by its id attribute, which should be unique within the page. It returns a single element.

Example:

JavaScript
let heading = document.getElementById("main-title");
console.log(heading.textContent);  // Output: Welcome to My Website

This method is efficient and straightforward, but it can only select one element since id is unique.

querySelector() is more flexible and can select elements using any CSS selector (#id, .class, or tag). It returns the first matching element.

Example:

JavaScript
let firstParagraph = document.querySelector("p");
console.log(firstParagraph.textContent);

This method selects all elements that match a specific CSS selector and returns a NodeList, which is an array-like structure.

Example:

JavaScript
let listItems = document.querySelectorAll("li");
listItems.forEach(item => console.log(item.textContent));  // Loop through all <li> elements

You can loop over the NodeList using forEach to access each element individually.