JavaScript is one of the foremost widely-used programming languages. JavaScript is mainly used to create dynamic web pages. Initially, it could be used only in browsers. Every browser has an embedded JavaScript engine that can execute JavaScript code. The JavaScript engine in Google Chrome is called v8, and the one in Mozilla Firefox is called SpiderMonkey. In 2009, Ryan Dahl created Node.js. He took the v8 engine and embedded it inside a C++ program. With node.js, we can now use JavaScript outside of a web browser.
JavaScript engines are now important components of many servers and a variety of applications. Once mocked as a toy language by programmes, it is now used everywhere. You can now create full-blown mobile and web apps with it. It is also used to create command-line tools.
JavaScript is often confused with Java. Both of them are programming languages, but they differ significantly in design.
The History of JavaScript
In 1993, Mosaic was released. It was the first browser that could be used by ordinary people. This led to the spread of the world wide web. The creators of Mosaic later developed a new browser – Netscape Navigator. Back then, web pages were static. They lacked the dynamic features that today’s web pages do. They were not interactive.
To make web pages dynamic, Netscape Navigator decided to add a scripting language to them. Brendan Eich was given this responsibility. He created a new language called Mocha. It was later named LiveScript and then, as a marketing trick, renamed JavaScript to cash in on the popularity of the Java programming language back then.
Microsoft released a new browser—Internet Explorer. They reverse-engineered Netscape’s JavaScript and developed JScript. There were significant differences between the two. That’s why earlier web pages were either “best viewed in Internet Explorer” or “best viewed in Netscape Navigator”. Netscape worked with ECMA International (European Computer Manufacturer’s Association) to standardise JavaScript, which led to the creation of ECMAScript.
In 2008, all the different parties came together to combine all their work and drive the language ahead. This resulted in the ECMAScript 5 standard. JavaScript is now the most extensively used and fastest-growing programming language in the world.
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What is JavaScript used for?
JavaScript is used to create dynamic and interactive web pages. HTML and CSS can only make static pages. When you move your cursor around a static page or click anywhere on it, nothing happens except when there’s a hyperlink. In dynamic pages, the web page responds to the user’s actions. For example, a dropdown menu appears when you move your cursor over the menu button. You can zoom in and out of a dynamic web page. Audio, video and animations can be played on the web page.
The following are some other ways JavaScript can be used to make a web page interactive with the user:
- The button changes its colour when the cursor hovers over it.
- Slide through a carousel of images
- Displaying a count-down timer on the website
- Displaying the date and time
- To create forms that respond to user actions
- Validating user input before submitting the form
Most popular websites use JavaScript, including Facebook, Google, and Youtube. You can develop apps for mobile and the web using JavaScript using frameworks. Google Maps is one such example. It can be used to build web servers and develop back-end infrastructure using node.js. JavaScript is also used to create in-browser games. Some of the popular games built using JavaScript are Angry Birds, 2048, Crosscode, and Polycraft.
How does JavaScript work?
Everything in JavaScript happens inside the “execution context”. Execution context is the ultimate place for running every single line of code. It consists of the execution code of currently performing (running) code and all the rest of the upcoming code lines of execution. The execution context has two parts:
- Variable Environment (Memory) Here variables and functions are stored as key-value pairs.
- Thread of Execution (Code) – This is the place where code is executed one line at a time.
JavaScript is a synchronous, single-threaded language. That means it can execute one command at a time in a specific order. The execution happens in two phases:
- Memory creation phase – Here memory is allocated to variables and functions inside the execution context.
- Code execution phase – Here the commands are executed in the order they appear.
Call stacks are used to keep track of where you are in the program. The call stack is also known by other names like the execution content stack, programme stack, control stack, runtime stack, and machine stack. A global execution context is created when you start a JavaScript program. And when a function is invoked, a new execution context is created inside the global execution context. This new execution context is then put on top of the stack. And when we return from the function, it is removed from the top of the stack.
[Also Read, JavaScript Coding Interview Questions and Answers]
[Also Read, React JS Tutorial for Beginners]
Frameworks and Libraries
JavaScript libraries are libraries of pre-written code snippets that can be used to perform common JavaScript functions. It allows for the easier development of JavaScript-based apps. Some libraries allow the integration of JavaScript with CSS, PHP, and Java. While others allow the use of JavaScript functions to make complicated and repetitive tasks easier to execute.
jQuery has been prominent to date and is the most popularly used JavaScript library. Facebook created a JavaScript library called React. It helps developers build user interfaces. It is used by almost all popular companies like Facebook, Netflix, Instagram, Twitter, Uber, etc.
The JavaScript framework is a full toolset that helps shape and organise your website or applications and to build websites or web applications too. Angular JS is a JavaScript framework created by Google that was widely used to create web apps. React Native is a framework that is used to create mobile apps. It was created by Facebook. Bootstrap, Aurelia, and Vue.JS are some of the other commonly used frameworks.
The difference between libraries and frameworks is that libraries can be called on an “on-use” basis, whereas a framework provides you with all the tools you need and a framework to build your app around. Libraries allow freedom since you can use them whenever you need them. Frameworks, on the other hand, have restrictions. Different frameworks are used for different purposes.
