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Complete Guide on JavaScript (JS)

What is JavaScript? Complete Guide

JavaScript may be one of the first concepts you hear when starting your career in software development. Moreover, you may have heard it even if that's not your field! And there are plenty of reasons for it! JavaScript is a powerful tool for creating dynamic, interactive websites and apps. Are you curious to know more about it? Let's start this exciting coding journey!

What is JavaScript?

JavaScript is a scripting language that definitely has recast web development. It's a lightweight, interpreted language that can run on any platform. JS is a client-side scripting language: it's executed by the client's web browser rather than on the server, which makes it highly versatile and capable of creating interactive software. Starting with JavaScript may seem difficult for beginners, but its learning curve is less steep than you think! With resources and practice, you can become a pro in no time. 

JavaScript Key Features

Input Validation. Since it can confirm user input for errors and validated fields, it's handy when handling forms. This feature can make dev teams save time and costs. 
Greater Control. It lets users create script functions while performing basic calculations. 
Platform Independence. Due to this feature, JavaScript can work on any operating system. It also has built-in functions to handle dates and times and to create dynamic HTML content. Its concept of independence also allows JS to detect the user's browser and OS!

How to use JavaScript?

With all the available resources, diving into JavaScript is easier than ever! Here are some steps to start:

1. Learn the basics. Like with everything, starting with the basic concepts can give you a greater understanding. In JS, the basics include data types, functions, and control structures. The Mozilla Developer Network has remarkable, extensive documentation on all this! 
2. Environment Selection. Once you master the basics, you should choose where to run your JavaScript code. Tools like Deno can run your code if you use JavaScript for server-side dev.
3. Code Writing. After choosing your environment, you can start writing your JavaScript code. You can use a text editor or an IDE to write and save your code with .js extension.
4. Code Running. There are different methods to run JavaScript code according to your chosen environment.  If you run your code in a browser, you can include your JavaScript file in an HTML page using a <script> tag. Contrariwise, if you run your code on a server with Node.js, you can use the node command followed by the name of your file to execute your code.

JavaScript Syntax and Structure

Here are some basic examples of JavaScript syntax, structure, and usage:

1. JavaScript Variables

You can declare variables using the var, let, or const keywords in JS. For example,

 var x = 10;
 let y = 20;
 const z = 30;

2. JavaScript Data Types

JavaScript has several built-in data types, like numbers, strings, booleans, arrays, and objects.

 let num = 10//number
 let str = 'Hello';;  //string
 let num = true;;  //boolean
 let arr = [ 1, 2, 3];;  //array
 let obj = { x: 1, y: 2};;  //object

3. JavaScript Control Structures

JavaScript has several structures for conditional execution and loops. Some JavaScript control structures examples include if/else, for, and while. For example:

 if (x > y) {
  console.log ('x is greater than y');
 } else {
  console.log ('x not is greater than y');
 for (let i = 0; i < 10; i++) {
  console.log (i);
 while (x < y) {
  console.log (x);

When to use JavaScript?

JavaScript is an all-around language that can work in various scenarios. Also, it can work in multiple situations to enhance the User Experience and add functionality. Here are some common scenarios and everyday use cases where you might want to use JavaScript.

JavaScript for Front End Development

One of JS's most common uses is for Front-End Development, specifically to create interactive and dynamic UIs. Its structure allows it to manipulate the Document Object Model (DOM), handle user input, and make asynchronous requests to a server.

JavaScript for Back End Development

With the help of Node.js, JavaScript is also quite functional for Back End purposes! This runtime environment allows devs to run JavaScript on the server side. As a result, you can build full-stack applications using only JavaScript! You can find great examples of this feature in projects made with the MERN Stack.

JavaScript for Mobile App Development

Like with back-end dev, you can also lean on JavaScript for native mobile apps! In this scenario, you can add libraries like React Native to create applications for both iOS and Android.

JavaScript for Server-Side Development

On the server side, you can use JavaScript and Node.js frameworks to build web applications with server-side rendering. Likewise, you can use JS to develop RESTful APIs for other applications to interact with your server. Further, you can connect JS with your preferred Database Management System (DBMS) and perform, among others, CRUD operations.

Why use JavaScript?

JavaScript works for a variety of tasks. Developers use it due to its dynamism in displaying formatting content. It can also work for other jobs, including Mobile Development, Progressive Web (PWAs), and Single-Page Applications (SPAs).

Another JS keynote is that it lets you install features like timely updates and interactive maps on the web. JavaScript also enables you to animate 2D/3D graphics. JavaScript is one of the few programming languages that can work in every popular browser. If you're looking to create a web page that works in all browsers, JavaScript is your ally!

JavaScript can dynamically update content without requiring the user to refresh the page. That can be useful for displaying real-time information or for creating single-page applications. Also, JS allows the addition of interactive elements, such as drop-down menus, pop-up windows, and hover effects. Last but not least, it's also great for adding animated elements, such as fading in and out or moving parts around. All these features are code-based, which means that once you deploy them, you shouldn't worry about the outcome of each interaction!


If you want to explore the power of JavaScript, there's no better time to start now. With countless online resources, you can quickly get started with the language and learn at your own pace. There's always something new to discover, from basic notions such as variables and loops to more advanced concepts like object-oriented programming. So, whether you're a beginner or an experienced developer, take the time to explore the power of JavaScript and see what it can do for your next project!