JavaScript: Difference between revisions

'''JavaScript''' is a high-level, dynamic, untyped programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. It was originally developed by Brendan Eich in 1995 while working at Netscape. JavaScript allows developers to create interactive web pages and is an essential part of web applications. It supports object-oriented, imperative, and functional programming styles. Over the years, JavaScript has evolved and increased in complexity, becoming a robust language that can be used for various applications beyond web development, including server-side programming, mobile app development, and even game development.

JavaScript was conceived by Brendan Eich, who created the first version of the language in just ten days in May 1995. Initially named Mocha and later changed to LiveScript, it was finally dubbed JavaScript to exploit the popularity of the Java programming language at the time. It was first implemented in Netscape Navigator 2, which was released in 1995.  

The language gained traction quickly due to its ability to facilitate interactive features on websites that were otherwise static. In 1996, Microsoft introduced JScript as a competitor within its Internet Explorer browser, leading to a period of fragmentation as different browsers began to support various dialects of JavaScript.  

In an effort to standardize the language, the European Computer Manufacturers Association (ECMA) adopted JavaScript as the official standard, resulting in the creation of ECMAScript. The first standard, known as ECMA-262, was published in June 1997. Subsequent revisions have introduced many features, including modules, classes, and asynchronous programming.

=== Evolution through Standards ===

Since its inception, JavaScript has undergone several iterations synchronized with ECMAScript updates. Significant releases include ECMAScript 3 (1999), which solidified the language's syntax and established a solid foundation; ECMAScript 5 (2009), which introduced many new features such as strict mode, JSON support, and new array methods; and ECMAScript 6 (2015), commonly referred to as ES6 or ES2015, which brought a massive set of updates including arrow functions, classes, template literals, and modules.  

Every year since ES6, new proposals have been introduced and adopted under the annual update process managed by TC39, the committee responsible for evolving JavaScript.

JavaScript is primarily executed on the client-side within web browsers, but its architecture allows for execution in other environments as well, such as Node.js for server-side applications. The language's design supports event-driven programming, making it ideal for web applications that require responsiveness to user inputs.

=== Execution Environment ===

JavaScript code is executed in an event-driven, non-blocking manner through a mechanism called the event loop. The event loop continuously checks for events or messages to be processed, allowing developers to write code that can respond to user actions while maintaining the performance of the web application.

The language operates within the context of a runtime environment, which provides functions and objects that interactive applications can use. For instance, when JavaScript runs in a web browser, it interacts with the Document Object Model (DOM) to manipulate the HTML elements of a web page.

JavaScript supports first-class functions, meaning that functions can be treated as values. This aspect allows functions to be passed as arguments, returned from other functions, and assigned to variables. Furthermore, JavaScript has a dynamic typing system, enabling developers to assign and manipulate various data types without explicit declarations.

 

The language also supports prototypal inheritance, which allows objects to inherit properties and methods from other objects. This inheritance model contributes to the flexibility and modularity of JavaScript code.

JavaScript is widely implemented across modern web browsers, with virtually all of them supporting it natively. As a result, it has become an essential tool for front-end development. Additionally, JavaScript can be used on server-side platforms like Node.js, enabling full-stack development using a single programming language.

=== Browser Support ===

Modern web browsers, such as Google Chrome, Mozilla Firefox, Microsoft Edge, and Safari, have robust support for JavaScript based on ECMAScript standards. Each browser includes a JavaScript engine – such as V8 for Chrome, SpiderMonkey for Firefox, and JavaScriptCore for Safari – which parses and executes JavaScript code, providing a consistent environment for web development across different platforms.

=== Server-Side Development ===

JavaScript's rise in popularity for server-side development has been facilitated through the advent of Node.js, an open-source runtime environment built on the V8 engine. Node.js allows developers to run JavaScript on the server, which opens new avenues for creating dynamic web applications, managing databases, and performing file operations outside the browser.

Node.js also employs an event-driven, non-blocking I/O model, making it efficient for handling multiple connections simultaneously. As such, it is commonly used to build APIs, microservices, and real-time applications.

JavaScript is utilized in a myriad of applications ranging from front-end to back-end solutions. Its versatility makes it one of the most widely adopted programming languages in the development community.

Single Page Applications (SPAs) have become a standard architectural pattern that leverages JavaScript, providing seamless user experiences by loading content dynamically without requiring full page reloads.

JavaScript can also be applied to mobile application development thanks to frameworks like React Native and Ionic. These frameworks allow developers to build cross-platform mobile applications using JavaScript, thereby reducing the learning curve and resource expenditure typically associated with native mobile development.  

 

In recent years, JavaScript has found its place within the gaming industry. Engines such as Phaser and Babylon.js provide libraries and tools for creating both 2D and 3D games that can run in web browsers. The ability to run games directly in the browser without any additional plug-ins has made JavaScript a popular choice for indie game developers and studios.  

Despite its popularity, JavaScript is not without criticism. Issues regarding language quirks, security vulnerabilities, and performance can affect the developer experience and the security of applications.

 

 

JavaScript's dynamic nature can lead to unexpected behavior, especially for developers who come from statically typed languages. Common pitfalls include type coercion, the use of “==” for equality checks (which performs type conversion), and the use of closures that may lead to unintended consequences, such as the loss of context.

 

While many of these quirks can be mitigated through effective practices and modern development tools, they can still create obstacles for beginners and seasoned developers alike.

JavaScript is also susceptible to security vulnerabilities, most notably Cross-Site Scripting (XSS) attacks, which occur when an attacker injects malicious code into a website that is trusted by users. Furthermore, JavaScript code can be viewable by anyone since it is executed client-side, making it a target for reverse engineering and exploitation.

Though various strategies and frameworks exist to enhance security, developers must consistently be aware of these risks and adopt best practices to protect their applications.

* [[JSON]]

* [[TypeScript]]

* [[WebAssembly]]

* [https://developer.mozilla.org/en-US/docs/Web/JavaScript JavaScript on MDN]

* [https://www.ecma-international.org/publications/standards/Ecma-262.htm ECMA-262 Standard]  

* [https://nodejs.org/en/docs/ Node.js Documentation]

* [https://playcanvas.com/ PlayCanvas Game Engine]

[[Category:Client-side scripting]]