What is JavaScript?

You can’t get far in tech without running into javascript, and chances are you’re here right now because you’re interested in learning about it. JavaScript is one of the most powerful tools a web developer can have in their arsenal. It’s used to make websites and apps dynamic and interactive. It’s responsible for a lot of the visual effects we take for granted, such as when you hover over an image and it zooms in or changes or when Google suggests search terms based on a few letters you’ve started typing.

In short, javascript is the heart of your website’s functionality. Think of HTML as the skeleton and CSS as the muscular and nervous system that makes your website look beautiful. JavaScript is the brain, liver and kidneys of your site that makes it function and respond to user actions.

When you open a page in your browser, it’s loaded with HTML and CSS, but then javascript gets called in to make the page dynamic and responsive. This is also known as client-side code, since it’s running on the user’s computer.

JavaScript is a programming language that was originally developed by Netscape to add interactivity and dynamic features to early versions of the World Wide Web. It has since evolved into an independent programming language with its own specification, ECMAScript. It can run on any operating system, but it’s most popularly used in web development to add interactivity and functionality to websites.

Unlike other programming languages, such as C and C++, JavaScript is compiled into machine code as it executes, which is called just-in-time compilation. This allows it to be executed quickly, especially for simple functions and processes. It’s this power that allows javascript to be used in front end and back end web development as well as in mobile applications.

When a javascript code snippet is passed into the engine, it’s parsed and compiled into an abstract syntax tree (AST) and then converted to machine code using the execution context. This machine code is then interpreted by the processor and executed.

In the first phase of the execution, it scans through the code line by line and assigns memory to each variable. For example, if a variable is defined as a number such as num 2 or square2, the value of that variable will be calculated by the function, and the result will be assigned to the variable. Once the function completes its work, it will destroy its execution context and then return the result.

Another thing to note about JS is that it’s single-threaded, so only one instruction can be executed at a time. For this reason, it’s not recommended to use a large amount of complex and synchronous code in a webpage or app. This can cause the app to become slow and unresponsive. Instead, it’s best to use asynchronous code when possible. This will prevent the app from becoming sluggish and will allow users to interact with the site faster.