JavaScript and Client-Side Code

JavaScript is a high-level, dynamic programming language that is primarily used to create interactive and dynamic user interfaces on the client-side of web applications. It is a scripting language that is interpreted at runtime by the web browser, which means that JavaScript code is executed on the user’s machine, rather than on the web server.

Some of the key features and capabilities of JavaScript include:

Manipulating HTML and CSS – JavaScript can be used to manipulate HTML and CSS, allowing developers to dynamically modify web page content and appearance.

Event Handling – JavaScript can be used to handle user events such as clicks, keystrokes, and mouse movements, enabling developers to create interactive and responsive user interfaces.

Asynchronous Programming – JavaScript supports asynchronous programming, which allows developers to execute multiple tasks simultaneously and avoid blocking the main thread.

Object-Oriented Programming – JavaScript supports object-oriented programming (OOP) principles, allowing developers to create reusable and maintainable code.

APIs and Libraries – JavaScript has a vast collection of APIs and libraries that enable developers to add complex functionality to their web applications, such as data visualization, animation, and geolocation. In addition to JavaScript, there are other client-side technologies that are commonly used in web development, such as HTML, CSS, and jQuery. HTML is used to structure web page content, while CSS is used to style and layout web page elements. jQuery is a JavaScript library that provides a set of tools and utilities for simplifying and streamlining JavaScript development.

Modern browsers understand an internal programming language called JavaScript. When the browser encounters JavaScript code inside an HTML page, it runs the program’s instructions. The browser (the client) doesn’t need a connection to the server to run JavaScript code —it’s completely independent. Client-side script uses the processing power of the computer on which the browser is running. That’s a tremendous advantage because it takes the pressure off the Web server and distributes tasks to individuals.

Client-side scripting becomes complicated — and extremely powerful —when combined with logic on the server. Imagine this scenario: The Web server sends a stream of HTML that contains JavaScript instructions. Those instructions include JavaScript code that checks whether the anonymous user has typed a number from 1 to 10 in a text box. The browser sees the script and executes it locally. Until the user has typed a number from 1 to 10, the Web server isn’t involved. When the browser sends the number back to the Web server, the return action is known as a postback.