What is a JavaScript engine and how does it work?

• A JavaScript engine is a program that interprets and executes JavaScript code.

• JavaScript engines are typically built into web browsers, and they are responsible for running JavaScript code on web pages.

• JavaScript engines can also be used in server-side environments, such as Node.js, to execute JavaScript code on the server.

A JavaScript engine works by following a series of steps to interpret and execute JavaScript code:

• Parsing: The JavaScript engine reads the source code and converts it into an Abstract Syntax Tree (AST), which represents the structure of the code in a format that can be understood by the engine.

• Compilation: The engine then compiles the AST into bytecode or machine code, depending on the type of engine being used. Some engines use a just-in-time (JIT) compiler to optimize performance by compiling frequently used code on-the-fly.

• Execution: The compiled code is executed by the engine, following the instructions in the code to perform the desired tasks.

• Garbage Collection: As the program executes, the JavaScript engine keeps track of objects and memory usage, and it performs garbage collection to free up memory that is no longer needed.

• JavaScript engines can vary in terms of their performance and features, and different engines may be optimized for different types of applications. Some of the most popular JavaScript engines include V8 (used in Google Chrome and Node.js), SpiderMonkey (used in Mozilla Firefox), and JavaScriptCore (used in Apple Safari).

• Overall, a JavaScript engine is a critical component for executing JavaScript code, and it plays an important role in determining the performance and capabilities of JavaScript applications.