JavaScript is a popular scripting language that allows developers to build dynamic websites and applications. It’s one of the most popular languages used in front end web development, and it’s also useful for creating back end infrastructure like databases.
Originally developed in 1995, JavaScript was designed to be lightweight and simple, but it soon proved to be a powerful tool for adding interactive elements to web pages. It’s now one of the most widely used languages on the Internet and can be found in most major browsers.
It’s a fast, versatile, and widely used scripting language that can be easily learned and implemented by beginners. It’s also a great way to create user-friendly, responsive web pages that are easy for users to navigate and interact with.
What is a JavaScript Engine?
The JavaScript engine is a part of the web browser that reads and executes JavaScript code. It’s also responsible for translating the JavaScript code to HTML and CSS to display on a web page.
When a web page loads, the browser parses the HTML to create a document object model or DOM. The DOM presents the live view of the web page to the JavaScript code, and it also lets developers grab information from images and other elements that are linked to the HTML.
Once the DOM is created, the JavaScript engine will read the JavaScript code and execute it in the context of the DOM. It does this by executing the code in what’s called a call stack.
A call stack is a stack of functions that the JavaScript engine calls during execution, and it is important to understand how this works because you might have to use it to make your application work smoothly. When you have a function that takes a long time to complete, it can cause the JavaScript engine to block and stop running other code.
It’s also possible to enqueue a callback function on the main thread when the event loop is completed, which lets the JS engine offload the long-running task to the main thread while it awaits for the synchronous code from your JS functions to finish. This can speed up UI performance and ensure that users always have a smooth, uninterrupted experience.
In addition to speeding up UIs, Event Loops are also helpful because they allow JS to offload long-running tasks to the main JS thread. This can free up the JS engine to run other asynchronous code, which is often needed for things like server-side processing.
When a function is executed, the JavaScript engine will create a global execution context in memory. This context contains all the data and variables that are being used by the function. It’s also where JavaScript executes the nested functions that it needs to perform in order to complete its task.
After creating the context, the JavaScript engine will assign memory to each variable that is being used by the function. This process is repeated for all the variables that are being used by the function, until the function is completed.