What is JavaScript?

JavaScript is a popular scripting language that allows you to build complex features on web pages. Whenever a web page does more than sit there and display static information, like displaying timely content updates, animated 2D/3D graphics, interactive maps, , scrolling video jukeboxes, JavaScript is almost certainly being used. It is the third layer of the layer cake of standard web development technologies, the first two of which are HTML and CSS.

JavaScript History 

Brendan Eich developed JavaScript at Netscape Communications in 1995. Netscape and Eich created JavaScript as a scripting language for use with Netscape Navigator, the company's flagship web browser.

Following its release, an increasing number of browsers began to support JavaScript. Nonetheless, for much of its history, JS was not regarded as a serious programming language. Its early releases had significant performance and security issues, but developers had no choice. They had to use JavaScript if they wanted to run programs in the browser.

The release of Google's open-source Chrome V8, a high-performance JavaScript engine, in 2008 marked a watershed moment for JavaScript. The subsequent proliferation of fast JavaScript engines enabled developers to create sophisticated browser-based applications that competed with desktop and mobile applications in terms of performance. Soon after, Ryan Dahl released Node.js, an open-source, cross-platform environment. It allowed you to run JS file from outside of a browser.

JavaScript can now be used to create various applications, including browser, server, mobile, and desktop applications. JavaScript is used in the products of the majority of major online companies today, including Facebook, Twitter, Netflix, and Google.

Why JavaScript?

JavaScript can make a website more interactive, and its user-friendliness aids in website navigation and allows designers to guide visitors with additional information or walkthroughs. JavaScript can also be used to create visual effects. JS can also be used effectively to create special effects such as image rollover.

JavaScript can run web pages and external applications such as PDF documents, widgets, and flash applications. JavaScript has exploded in the web development industry, and there are no web technologies that do not use JavaScript.

JavaScript's importance cannot be overstated, as it can function as both an object-oriented and a procedural programming language. Due to functional programming concepts, JS functions are first-class objects. Furthermore, prototypal inheritance, modules, namespaces, anonymous (lambda) functions, and even metaprogramming are among its advanced features. In addition, Javascript can create full-fledged applications such as Gmail and Google Maps.

What Does a JavaScript Developer Do? 

A JavaScript Developer is one who specializes in the design, testing, and implementation of software in JavaScript. JS should not be confused with Java; despite their similar names, the two programming languages are very different. JavaScript is one of the best scripting languages as it allows users to create dynamic content, control multimedia, animate images, and perform various other tasks.

With that said, here are some common responsibilities of a JavaScript developer:

• Create long-lasting code that can be modified and scaled.
• Check that the UI/UX designs are practical.
• Improve the performance of the primary front-end or back-end.
• Change the specifications and designs of complex applications.
• Examine the JavaScript code, the requirements, the system risks, and the dependability of the software.
• Collaborate with front-end and back-end web developers.

JavaScript developers are in charge of a website's programming, development, and implementation, and they may have to juggle a variety of programming tasks. For example, they may be in charge of an entire website or specific aspects or pages of one or more websites. As a result, JavaScript language is primarily used in web-based applications and web browsers. In addition, it is quite popular and frequently used in applications other than the Web, such as software, servers, and embedded hardware controls.

How to Become a JavaScript Developer? 

Learn the Basics of JavaScript

While frameworks are useful, learning the fundamentals of plain JS can also be beneficial. Learn JavaScript fundamental concepts such as closures, scopes, syntax, and prototyping.

Complete JavaScript Certifications

While a college education is beneficial, you should also consider obtaining JavaScript certification. You can obtain various reputable certifications to demonstrate your understanding of this programming language. While pursuing a JavaScript course, you will watch a JavaScript tutorial or two, which will help you learn JavaScript. This will further hone your JavaScript skills.

Find a Mentor

Finding a mentor is one of the most beneficial things you can do to help you become a JavaScript developer. A mentor is an experienced professional who can guide your progress as you complete individual coding projects. In addition, they can point out more efficient ways of writing JS code and walk you through difficult JavaScript concepts.

Gain Experience

You can apply for a job or internship after learning the fundamentals of JavaScript language through formal education, certificate programs, or mentorship. Your first job may be as a junior web developer, where you can gain relevant experience. As your experience grows, you will be able to qualify for more responsible roles.

Familiarize Yourself With Various Frameworks.

JavaScript users can work with various related technologies, mainly frameworks. These frameworks include predefined functions and classes that improve the efficiency of JavaScript. Today's most popular JS frameworks are React, Angular, Vue JS, Ember JS, and Node JS.

Refresh Your HTML and CSS Knowledge

HTML and CSS are two of the most basic aspects of coding. Because all JavaScript frameworks rely on HTML and CSS, you can benefit greatly from brushing up on your knowledge of them.

Advantages of JavaScript

Simple 

JavaScript is easy to understand and learn. The structure will be simple for both users and developers. Furthermore, it is simple to implement, saving web developers a lot of money when creating dynamic content.

Fast

Because JavaScript is an "interpreted" language, it reduces the time required for compilation in other programming languages such as Java. JavaScript is another client-side script that speeds up program execution by eliminating the wait time for server connections.

In addition, it is always run in a client environment, regardless of where it is hosted, to reduce bandwidth usage and speed up execution.

Interoperability

Because JavaScript integrates so well with other programming languages, many developers prefer to use it to create a wide range of applications. It can be found on any webpage or in a script written in another programming language.

Scalable

Because JavaScript is client-side, data validation can be performed within the browser rather than being sent to the server. In the event of a discrepancy, the entire website does not need to be reloaded. Instead, the browser only updates the selected area of the page.

Installation of JavaScript

It is simple to get started with JavaScript. You can start writing JavaScript in your browser console right now!

The web browser was the first JavaScript runtime environment and remained the most popular. JavaScript in the browser is far more common than JavaScript in other places. Almost every browser includes a JavaScript engine.

JavaScript in the browser serves two primary functions: programmatically altering web pages based on user actions and communicating with a server over a network. The first task requires the programmer to use an API to manipulate the structure and appearance of the HTML page. Next, they require an API that allows them to use the operating system's ability to send and receive messages over a network for the second task. Almost every browser has a way to accomplish these tasks, though there are some browser compatibility issues.

The DOM (Document Object Model) API allows you to change the structure and appearance of a web page, whereas the XHR (XMLHttpRequest) interface and Fetch API allow you to communicate with a server.

Components of JavaScript

The JavaScript runtime in the browser contains an implementation of JavaScript that allows developers to create web applications. The web browser's runtime includes three critical components:

1. The Core Based On ECMAScript 
2. Document Object Model (DOM)
3. Browser Object Model (BOM) 

Core IO Functions

JavaScript is an ECMAScript implementation, and all web browsers must adhere to ECMAScript when developing their JavaScript engine and runtime environments. ECMAScript does not include any IO functions; instead, JavaScript implements the various functions according to the guidelines established by ECMAScript. However, ECMAScript and JavaScript are not the same thing. ECMAScript is a scripting language not dependent on web browsers and based on the standards defined in ECMA-262. JavaScript is a robust scripting language built on ECMAScript.

Document Object Model

The Document Object Model is a language-independent interface for XML and HTML that maps out the entire document as a tree-like hierarchy of nodes. The HTML code provided below is an example of a node hierarchy.

<!DOCTYPE html>
<html>
  <body>
    <h1>heading</h1>
    <h2>subheading</h2>
    <p>paragraph.</p>
  </body>
</html>

Browser Object Model

Similar to how the DOM is an interface for interacting with the document, the Browser Object Model is an interface for interacting with the browser outside of the context of the document. The BOM was regarded as problematic because it was the only part of JavaScript that lacked a standard. However, with the release of HTML5, most of the BOM-related features became part of the official HTML5 standard, resulting in significantly reduced confusion surrounding the BOM.

The window object that represents the browser window can be used to access the BOM. The browser's window object contains all of the global variables. Let's look at how to access the window object and its properties:

Development Best Practices

Declare Variables on Top

All declarations should be placed at the beginning of each script or JavaScript function. This results in cleaner code and a single location to look for local variables. It will also make it easier to avoid undesirable global variables and reduce the likelihood of undesirable re-declarations.

let itemName, price, discount, fullPrice;

itemName = "Detergent";

price = 9.11;
discount = 1.5;

fullPrice = price - discount;

Initialize Variables

When you declare variables, you should always initialize them. This results in cleaner code, a single location to initialize variables, and the avoidance of undefined values.

let itemName = "";
let price = 0;
let discount = 0;
let fullPrice = 0;

let greeting="Hello world";

Declare Objects With const

Declaring objects with const will prevent any accidental change of type:

let item = {itemName:"Detergent", price:9.11, discount:1.5};
item = "Detergent"; // Changes object to string

const let item = {itemName:"Detergent", price:9.11, discount:1.5};
item = "Detergent"; // This change not possible

Comment Your Code Well

When you learn JavaScript programming, commenting is a hot topic. Some argue that it is unnecessary, but code without comments becomes difficult to read after a while. Overly long and verbose comments, on the other hand, are unnecessary because they will take more time to read and comprehend.

Comment your code, especially functions, classes, objects, and interfaces, but only include important information. Use tags such as

@constructor, @param, @version, @return, and others to keep your comments concise and easy to read.

Use for...of Instead of Normal for Loops

Loops can be expensive in terms of performance because they repeatedly perform the same operation. However, if they are optimized, they can run faster. Many JavaScript best practices exist to help you write more performant loops. For example, avoiding nesting, keeping DOM manipulation outside of loops, and declaring a separate variable for loop length.

Using the for...of loop rather than for is also a common JavaScript coding practice. This syntax was introduced in ECMAScript 6, and it includes a built-in iterator to eliminate the need to define the i variable and the length value:

// conventional for loop
let items = ["Detergent", "Polish", "Tissue"];
let itemCount = items.length;

for(let i = 0; i < itemCount; i++) {
console.log(items[i]);
}

// better practice
let items = ["Detergent", "Polish", "Tissue"];

for(item of items) {
console.log(item);
}

console.log("Hello World");

Prefer Class Over Constructor Functions

Although the constructor function allows you to do some very nice things, reaching for its prototype is a sign that you should use a class which is supported pretty much everywhere. It is simpler and more likely to be understood by the general public.

Use === Instead of ==

JavaScript uses two equality operators: === and !== are the strict equality operators, while == and != are the non-strict operators. It is considered best practice always to use strict equality when comparing.

However, when working with == and !=, you'll encounter different types of issues. When the values you're comparing have different types, the non-strict operators will try to coerce their values, and you may get unexpected results.