How Does JavaScript Work?
When it comes to web development, there are three elements to a site or project: structure (HTML), aesthetics (CSS) and functionality (javascript). Most developers begin their journey with HTML and CSS and then move on to JavaScript. javascript is the magical component that makes a website dynamic, and understanding how it works can be tricky. It is often described as being a high-level, single-threaded, garbage-collected, interpreted (or just-in-time compiled), prototype-based, multi-paradigm language with a non-blocking event loop. It’s a lot to take in and can be daunting for any beginner developer, but it is also crucial to understand how the language actually works to build robust applications that are fast and efficient.
Despite being so widely used, few people know how JS actually runs and what goes on behind the scenes to produce the final product in their browsers. In this blog post, we will break down the process of how a piece of javascript code turns into the HTML and CSS that is displayed on your screen.
The first thing that happens when a piece of javascript code is entered into the engine is that it is parsed. Parsing is a process that essentially reads the code and creates an abstract representation of it using a tree data structure. This tree is then stored and used to generate the bytecode that will run in the engine.
Once the javascript is in bytecode form it will then be executed by the engine. The engine will evaluate each line of the code and then use it to perform the desired function or operation. For example, the code if (document.querySelector(‘///’)) will compare the string iceCream to the string chocolate and determine if the two strings are equal. If the two are not equal, the next block of code will be executed which will likely be a test or an if statement that will compare the iceCream and chocolate variables again. If the variables are not equal, the second block of code will be executed which is likely an else statement.
Another interesting aspect of javascript is that it supports functions as the building blocks of applications. Functions are code blocks that do a particular task and can be chained together like regular code. When writing javascript code, if an expression looks like a variable name and is followed by parentheses, it is probably a function. Functions can accept arguments which are the input or output values that will be generated by the function.
The last aspect of javascript is that it can be used for both client-side and server-side programming. When it is used for client-side, the javascript will be embedded directly into an HTML file or referenced in a separate.js file and then downloaded when the page is viewed in a browser. This will be run along with the HTML and CSS to create a functional web page. Javascript is also supported by a large ecosystem of libraries and frameworks that can help speed up application development.