The current essay is devoted to the basic principles and introduction of JavaScript. This language no longer needs to be introduced since it has become integral to any web development. Everybody knows that JavaScript is not that easy to IGNORE. Read this article if you want to understand the core principles of Javascript from getting to know its key structure. And also you will know how it helps create MOVABLE, MORE INTERESTING, and TASTIC content.

For all the wannabe programmers out there, or if you want to improve your web programming prowess. This article will form a solid ground in Javascript targeting the relevant notions and ideas needed for web app development.

In the following section, you will understand what JavaScript is, so let’s move on to it.

What JavaScript Means

JavaScript is an interpreted, high-level programming that is used to build dynamic and interactive features on web pages.

Web browsers and page JavaScript web-interactive content and features. Such as multimedia, games, dynamic content updates, and validation, are made possible with this technology.

JavaScript is indispensable both on the client side and server side. It is on the client side that the script is executed in the browser. It enables interaction with the web page thus no page has to be loaded.

This therefore makes the websites easier and more pleasant to use. There also exists server-side scripting in which scripts are written in JavaScript using environments like Node.js to operate the server, databases, and web pages.

This makes JavaScript a tool that can be employed in the development process at both the front and the backend stages since both the front-end and back-end interphase with the application.

In the next section, you will take an overview of the JavaScript history.

JavaScript History

Before getting started in the history overview, JavaScript is only one language. And there is no language else to do its job, especially in the front-end stage. That’s all.

Before JavaScript, web pages were only static pages and were lacking for dynamic procedures. So they decided to develop a scripting language for the Netscape Navigator.

The Netscape team was thinking of collaborating with Sun Microsystems to use their Java Programming language with the Netscape tool. But that was failed for some unknown reasons.

They decided to hire someone else to do this task, he called Brendan Eich, and let me say, that was the greatest decision ever made in history.

Brendan Eich started the task and generated the first version of the scripting language in 1995 and embedded it into the Netscape version 2.

Live Script

The language syntaxes were similar to syntaxes of the Java programming language, and its interpreter was called “LiveScript”.

Eich was thinking of The name for his new scripting language. At this time Java was in hot demand and its popularity was officially spread. So he named his new scripting language with JavaScript name. And that was for a marketing ploy.

JScript

Microsoft takes over to generate its new Internet Explorer browser and that start a new war for browsers, against Netscape Navigator company.

Microsoft team released their scripting language in 1996 to embed it with Internet Explorer, they named it “JScript”.

This version supported HTML markups and CSS.

During this period, most of the developers weren’t able to develop their websites in two browsers to have the same design in both. It was a big change in the design and structures of two both.

So, this point leads Netscape and Microsoft to create other attractive sentences and slogans to do a ploy marketing for each other.

Netscape used the slogan “best viewed in Netscape”, while Microsoft used “best viewed in Internet Explorer”.

ECMA Script

To finish the slogan war. The Netscape company created a standard specification for the first ECMAScript language, and that was in 1997.

During several years, they released many versions of the ECMAScript language each year with a new version starting in 1998 and ending in 2000 with the name ECMAScript 4.

But Microsoft was not standing idly because its Internet Explorer was in spread. They reached 95% of the market.

That means Microsoft JScript became the standard specification for the client side of the web application.

In 2000 the ECMAScript was stopped with version 4. Because JScript became more popular than ECMAScript, Microsoft won.

ECMA Script and Macromedia

In 2004, Mozilla continued the challenge and released their new browser called “Firefox”, they improved this browser with ECMAScript 4 of the Netscape Navigator and did many other features according to the ECMA International standard.

This browser started to spread, and it became challenging for Google company and Microsoft.

V8 JavaScript Engine

In 2008 Google started a new challenge and released the Google Chrome browser with its v8 JavaScript engine. This browser was faster than Google Chrome competitors. Because they were dependent on just-in-time compilation.

In the next section, we will focus on the V8 JavaScript engine of the Chrome browser. Let’s dive right in.

How the V8 JavaScript Engine Works

V8 engine is a Google project which is an open source created to do a high performance for the JavaScript programming language.

The V8 engine is written in C++ programming language and implemented with two phases which are ECMAScript and WebAssembly.

Additionally, the v8 engine works with major operating systems such as Windows, macOS, Linux, and so many others.

Anyway, the mission of the V8 JavaScript engine is to translate the source code into binary bits (the machine code). And here, we are going to cover these phases. But before getting started, you have to know the difference between compiler and Interpreter.

The Lexical Tokens

The first step is receiving the source code from the server. Then it starts to analyze it according to some instructions in the lexical analysis and then generates a string containing the sequence of Lexical Tokens. This phase is also called a scanner.

The Parser

The parser receives the sequence of tokens and generates the Abstract Syntax Tree (AST) which represents those tokens in a big structure.

The Interpreter

Once it receives the AST, the Ignition interpreter starts to generate the bytecode and that was produced from the AST.

Then it sends bytecodes to TurboFan, and here TurboFan converts these bytecodes into binary bits which is the machine code.

On the other hand, the V8 engine has another thing called a Just-In-Time compiler to convert ECMAScript into native machine code before the execution.

The compiled code is another optimization or (re-optimized) to be a highly optimized binary bit or machine code.

If incorrect things are happening during this stage. It de-optimizes it and returns it to the interpreter to re-evaluate.

That was an overview of the V8 JavaScript engine work from the top. In next section, you will learn more about JavaScript Capabilities and Limitations.

Capabilities and Limitations of In-Browser JavaScript

Capabilities of In-Browser JavaScript

• Security Concerns: The Same-Origin Policy as well as other safety measures prohibits in-browser JavaScript from accessing sensitive information without authorization. However, it is still vulnerable to cross-site scripting (XSS) attacks if not handled properly.
• Browser Dependency: There is a strong reliance on the Browser’s Database Engine when executing JavaScript. This may bring up issues in terms of certain behaviors, or performance in different browsers, although most if not all circumvent such issues with modern browsers today.
• Performance Limitations: As earlier stated, JavaScript comes in a single thread, even though Web Workers allow some concurrency, so performance issues are inevitable in complex applications. Heavy processing activities can also affect the responsiveness of the application and lead to stutter.
• Limited File Access: Since the JavaScript code is executed within the browser, any scripts have no or very little access to the file system, chiefly because of security reasons. It can only handle files that are uploaded by the user through file inputs.
• Dependence on User Settings: JavaScript can be turned off by the users of the website where certain functions are implemented, and this may constrain the implementation of some features of the webpage. In such circumstances, developers should offer fallback measures.

Limitations of In-Browser JavaScript

• Safety Issues: The browser restriction on JavaScript, imposing the Same Origin Policy and other security measures, is to limit the exposure of sensitive information. That said, if not well managed, it still poses a risk of cross-site scripting (XSS) threats.
• Browser Dependency: The execution of JavaScript is dependent on the JavaScript engine built in the browser. This creates an inconsistency in the behavior or the performance of the different browsers, although quite a number of these issues have been addressed in modern browsers.
• Performance Bottlenecks: JavaScript is a single-threaded application (although Web Workers can provide some multi-threaded capabilities) which spells doom for most complex applications. High-end processes will usually thumb down the user interface and freeze the entire application.
• Limited File System Access: A JavaScript running in the web browser has substantially restricted access to the file system under normal circumstances and mainly for security purposes. It can only reach files that the user physically selects through file input elements.
• User Configurations Restriction: Certain aspects of JavaScript can be turned off by a user in their web browser which could limit some functionalities in the website. This is an eventuality that designers have to consider and make provision for.
• No Direct Access to Operating System Features: In-browser JavaScript cannot communicate with the underlying operating system as is the case with server-side languages or applications. This also makes it difficult to perform operations such as managing files, using hardware peripherals, and using the network stack.

In the next section, I am going to write a program with JavaScript. Only to show a dialog box with – a “Hello World !” message.

Write your First Program with JavaScript

Firstly, you have to install an editor to allow you to write the JavaScript code. And then copy the below code. Then open it in the browser.

<!DOCTYPE html>
<html>
  <head></head>
  <body>
    <script type="text/javascript">
      alert( "Hello World!" );
    </script>
  </body>
</html>

The result would be a popup box containing the – “Hello World !” message.

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