Explain V8 engine in Node.js

We will learn about the V8 engine, Node.js, and the connection between V8 and Node.js.

Overview of V8 JavaScript Engine

V8 is a high-performance JavaScript engine developed by Google and used in Google Chrome, the open-source browser from Google. It was designed to improve the performance of web applications by compiling JavaScript into native machine code rather than interpreting it, which makes it faster.

V8 is C++ based open source JavaScript engine. It runs on various platforms, like Linux, Windows, and macOS. It has features like just-in-time (JIT) compilation, garbage collection, and support for modern JavaScript features such as classes, Promises, and arrow functions, making it particularly well-suited for web browsers. It also supports WebAssembly, a low-level binary format for executing code on the web that is designed to be faster than JavaScript.

Modern web applications rely heavily on JavaScript for their functionality. So, V8 needs to be able to execute JavaScript code quickly and efficiently. To achieve this ability, V8 uses various techniques, such as hidden class optimization and inline caching, to make the execution of JavaScript code as fast as possible. Rhino, SpiderMonkey, Jerry script, etc., are some popular implemented JavaScript engines.

Some important components of the V8 javascript engine

These are some important components of the V8 JavaScript engine, making it a high-performance engine for node.js applications.

  • Garbage collection

  • JS interpreter

  • Web Assembly

Garbage Collector

V8 JavaScript includes a garbage collector. It frees up memory used by objects that are no longer needed. Memory leaks occur when an application creates objects but fails to release them when they are no longer needed properly. A garbage collector helps to prevent this memory leak.

JS Interpreter

In V8, Ignition first interprets JavaScript code, which is a bytecode interpreter. Ignition reads the code and evaluates it, performing the actions specified by the code. This is done quickly, but the bytecode generated by Ignition is not as efficient as machine code; this bytecode is passed to Turbofan, the optimization compiler of V8.

Turbofan analyses the bytecode and generates machine code for performance-critical parts of the code. This machine code is faster than the bytecode, but the compilation process can take longer. The compiled machine code is cached so that it can be reused if the same script is executed again, avoiding the need to recompile the code.

Using Ignition and Turbofan, V8 can quickly evaluate the code with a bytecode interpreter and then optimize the critical performance parts with the optimization compiler. This allows V8 to achieve high performance and efficient execution of JavaScript code.

Web Assembly

WebAssembly (often abbreviated as wasm) is binary instruction format for a stack-based virtual machine. In the V8 JavaScript engine, the WebAssembly code is executed by a Liftoff component. It is a WebAssembly-specific compiler designed to be fast, lightweight, and provide a smooth integration with V8. It's responsible for converting the binary wasm code into machine code and executing it.

Using Liftoff, V8 provides a fast and efficient way to run WebAssembly code alongside JavaScript, allowing developers to write code in multiple languages and run it efficiently on the web.

Connection between Node.js and V8

Node.js is a JavaScript runtime built on top of the V8 JavaScript engine. It allows developers to run JavaScript on the server to build network applications, using JavaScript as the programming language on both the front-end and back-end. Node.js uses V8 to execute JavaScript code on the server side. When a developer writes JavaScript code for a Node.js application, the code is passed to V8 for execution. V8 then compiles and executes the code, allowing the application to perform actions such as reading and writing files, making network requests, and interacting with a database.

The connection between Node.js and V8 is that Node.js uses V8 as its JavaScript runtime. Node.js provides an additional layer of functionality, such as libraries and modules, on top of V8 to support server-side programming in JavaScript.

Some Other Facts

Node.js was initially implemented with V8 as the JavaScript engine. The initial developers at Joyent chose to embed V8 because of its high performance and capability to handle the high concurrency that they believed would be required for building web servers.

While Node.js can technically work without V8, it would require significant development work. The developers would need to choose another JavaScript engine and modify the Node.js codebase to use it. Furthermore, the performance of Node.js would be greatly reduced without V8, and a lot of optimization would need to be done for the new engine. So, choosing another JavaScript engine might not be suitable. Therefore, it's very unlikely that Node.js will work without V8, as V8 is an integral part of the Node.js codebase and provides the high performance needed for most Node.js use cases.

Memory Related Issues

Currently, by default V8 has a memory limit of 512 MB on 32-bit systems and 1GB on 64-bit systems. This limit can cause issues if your Node.js process requires more memory than is available in a heap. For example, suppose you are trying to load a large dataset into memory or perform a complex computation. In that case, you may run out of memory and receive a “FATAL ERROR: JavaScript heap out of memory” error.

Some tips to Fix Memory-Related Issues

Look for ways to reduce the amount of memory your code is using. This could include reducing the size of data structures, caching frequently used data, or avoiding creating unnecessary objects.

To increase the available memory heap, use the --max-old-space-size command line flag when running a Node.js application.

Another solution is that if your dataset is too large to be handled by single node, you can consider breaking the data and running multiple instances of your script in parallel.

Note that performance impact can be different in different OS and environments.

Updated on: 17-Mar-2023


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