The Inner Workings of JavaScript
javascript is a programming language that allows you to interact with the web and create dynamic web pages. It has become a critical component in most websites and is used by web browsers to provide features like user interfaces, form validation, and other interactive elements. Despite its relatively low level of complexity, javascript can be quite powerful. This article will explore the inner workings of javascript so that you can understand what is happening behind the scenes when you visit a website and see javascript in action.
When you view a website on your computer, the server sends you a bunch of files, including HTML and CSS files. These provide the layout and design of the page. JavaScript makes it possible for the website to do cool things, like validating forms and creating visual effects. But how exactly does this code compile and execute in your web browser?
In order for a piece of javascript to run, it must first enter the JavaScript engine. Once it does this, the first thing that happens is that it is parsed. This process involves converting the raw code into a data structure that represents it, called an Abstract Syntax Tree (AST). This is done to make it easier for the JavaScript engine to read the code and detect errors in syntax.
After the AST is created, it will be translated into machine code and executed. This is done by using something called a call stack. The call stack is a way for the JavaScript engine to keep track of what function it is currently executing and what functions are being called by that function. It does this so that the correct machine code can be executed at each step of execution.
For example, if the first function in the sequence calls another function, then that function will enter the call stack and its own machine code will be executed. This will then execute the code that was originally entered into the AST, in this case a function to print(“Hi”)”.
When the code is being processed by the web browser, it is done so from top to bottom. This is because the call stack can block the browser from executing other code, so it must be processed first. As each block of code is processed, the variables that are used in that block are also being updated. This is why it is important to use var, let, and const keywords to define local variables rather than global ones.
If you are a web developer, you should know that frequent interaction and manipulation of the DOM slows down performance and can cause your site to appear sluggish. This is why techniques such as batching DOM updates and reducing function calls improve performance. By implementing these best practices, you can ensure that your javascript runs quickly and is running as efficiently as possible.