What is and how works the JavaScript Engine

What is a Javascript Engine?

A JavaScript engine is the part of the software that interprets and executes the JavaScript code. It is the core of every environment that executes JavaScript, environments like web browsers, Node.Js and others. The engine translates the JavaScript code into machine code or other lower-level code and executes it. This process allows the code to interact with the system and perform various tasks, such as manipulating the DOM in a web environment.

Key components of a JavaScript engine

  1. Parser: The parser reads the JavaScript code and turn it into an Abstract Sintax Tree (AST). The AST represent the code in a way that the engine can read it.
  2. Interpreter: The interpreter ejecutes the code line by line. In some engines this step can be omitted or improved by a Just-In-Time (JIT) compiler.
  3. JIT Compiler: The JIT compiler optimizes the code during execution by compiling it into machine code in real time. This allows for faster execution after the initial interpretation.
  4. Garbage collector: The garbage collector manages memory by automatically cleaning up memory that is not in use. It helps to prevent memory leaks and ensures efficient use of system resources.
javascript engine

Popular JavaScript engines

  • V8: Developed by Google, V8 is used in Google’s Chrome and Node.js. It is well known for its high performance, partly due to its powerful JIT compiler.
  • SpiderMonkey: Developed by Mozilla, SpiderMonkey is used in the Firefox browser. It was the first JavaScript engine and is still in continuous development.
  • JavaScriptCore (Also known as Nitro): Developed by Apple, JavaScriptCore is used in the Safari browser and other apps based on WebKit.
  • Chakra: Developed by Microsoft, Chakra was used in the Edge browser before the transition to a Chromium-based Edge, which now uses V8.

Importance of JavaScript Engines

JavaScript engines are crucial for the performance and efficiency of JavaScript applications. Advances in engine technology, such as JIT compilation and memory management, have significantly improved the speed and responsiveness of both web and server-side JavaScript applications.

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