9 Best JavaScript Runtime Environments for Better Code Execution

JavaScript has become the most popular programming language, powering web applications, servers, and more. The growth of JavaScript is fueled by flexible runtime environments that allow developers to execute JS code in different contexts.

In this comprehensive guide, we will explore the top 9 JavaScript runtimes available today. For each runtime, we will cover the key capabilities, best use cases, and reasons why thousands of developers trust them to build robust JS applications.

An Introduction to JavaScript Runtimes

Before diving into the specific options, let‘s briefly explain what a JavaScript runtime is and why it matters.

A JavaScript runtime provides the infrastructure and tooling required to execute JS code. It includes features like:

  • A JavaScript engine to parse and run JS code (e.g. V8, SpiderMonkey)
  • Web/browser APIs for access to functionality like DOM manipulation
  • Modules/libraries that expand the capabilities of the language
  • A process for managing asynchronous events/parallel execution

The runtime environment determines where and how JS code will execute. For example, a browser provides the runtime for front-end web JS. A server-side runtime allows executing JS on the backend.

Choosing the right JavaScript runtime brings access to specific features and performance optimizations for your use case.

Now let‘s explore the top options available today:

1. Bun – The All-In-One JavaScript Runtime

Bun describes itself as an "all-in-one JavaScript runtime" designed to boost developer productivity. The runtime combines a JavaScript engine, transpiler, bundler, and package manager into a single toolchain.

Key Features

  • Drop-in replacement for Node.js runtime
  • Faster performance via Zig language integration
  • First-class support for TypeScript
  • Ultra-fast watch mode to restart processes
  • Open source and community driven

Bun allows you to run server-side code, command line tools, scripts, and more. The runtime is focused on keeping compatibility with the enormous NPM ecosystem while modernizing everywhere else.

The combination of performance, TypeScript support, and simplified tooling makes Bun a good option for many server-side use cases from API backends to DevOps scripting.

2. Deno – A Secure JavaScript/TypeScript Runtime

Deno landed in 2018 as an alternative approach to Node.js. It‘s a JavaScript/TypeScript runtime built by Node‘s original creator that prioritizes developer experience, security, and simplicity.

Key Features

  • Secure by default through permissions-based APIs
  • Built-in TypeScript support
  • Integrated tools like a test runner and code linter
  • Consistent APIs between Deno in the browser
  • Single executable with no dependencies

A key motivation behind Deno is improving the security posture of JS/TS applications. Instead of Node‘s open access, Deno limits access to sensitive OS resources unless explicitly allowed.

This security focus combined with a fantastic dev experience makes Deno a top contender for building robust server-side applications.

3. Node.js – The JavaScript Runtime Juggernaut

Since its introduction in 2009, Node.js has become the most popular JavaScript runtime on the server. It revolutionized server-side development by enabling the creation of network applications with only JavaScript.

Key Features

  • Asynchronous and event-driven architecture
  • Cross-platform runtime
  • Enormous ecosystem of open source libraries/tools
  • High performance for I/O bound workloads
  • Package manager (NPM) with over 1.5 million modules

While Deno and Bun provide exciting new options, Node remains the industry standard – powering companies like Netflix, Uber, eBay, and more. The vibrant community and vast ecosystem make Node.js a safe choice for enterprise applications today.

Node continues to evolve by adopting cutting-edge JavaScript features like ESM (ECMA Script Modules). It strikes an impressive balance between stability and introducing new capabilities like worker threads.

4. Blueboat – A Serverless JavaScript Runtime

Blueboat offers a novel approach by providing a "serverless JavaScript runtime designed for the cloud". Instead of managing servers, Blueboat abstracts infrastructure through auto-scaling and distributed services.

Key Features

  • Built on V8 JavaScript engine + Rust
  • Automatic scalability across regions
  • Secure multi-tenant isolation
  • Data manipulation libraries included
  • Distributed system primitives

By leveraging cloud infrastructure, Blueboat can scale complex applications without provisioning physical servers. It caters towards teams that want to focus on code instead of cloud configuration.

The runtime suits modern apps that need to handle unpredictable traffic spikes or large amounts of data. Example workloads include real-time data streaming, IoT data pipelines, and multi-player gaming backends.

5. Napa.js – Multi-Threaded JavaScript Runtime

Napa.js brings multi-threaded execution to JavaScript through a pool of isolated V8 contexts. The ability to run code across threads and communicate between them provides compelling performance benefits.

Key Features

  • Multi-threading of JavaScript code
  • Wrapped as an NPM module
  • Backward compatible with Node.js
  • Communicate across V8 isolates

The creators designed Napa.js to accelerate parts of Microsoft Bing‘s services built on Node. However the project works great for any CPU-bound workload.

Good use cases for Napa.js include parallel processing of large datasets, blocking mathematical computations, and any task that performs better across multiple cores.

6. ChakraCore – Embeddable JavaScript Engine

ChakraCore serves a unique purpose among the runtimes covered. Instead of a complete runtime environment, ChakraCore provides the JavaScript engine separately through a C/C++ API.

Key Features

  • Multi-tiered architecture for performance
  • Supported on Linux, Windows, and macOS
  • Embeddable via documented C API
  • Diagnostics capabilities

Microsoft originally created the Chakra engine for its Edge and Internet Explorer browsers. By extracting it into an open source project, developers can integrate high-performance JS execution in C/C++ apps.

Embedding ChakraCore allows adding scripting capabilities or custom logic through JavaScript. This opens the door to some very creative mixed native/managed architectures.

7. WasmEdge – WebAssembly Runtime for Cloud-Native Development

WasmEdge offers a lightweight and extensible WebAssembly runtime designed for cloud-native workloads. It includes robust tooling for security, portability, and high performance across platforms.

Key Features

  • Sandboxed execution of WebAssembly
  • Language support for C, C++, Rust, JavaScript
  • Cloud-focused deployment and management
  • High efficiency across architectures

WebAssembly (WASM) has gained huge momentum as a compilation target from languages like Rust and C/C++. WasmEdge taps into this trend by creating a standardized runtime for running WASM at enterprise scale.

Use cases include offloading tasks across fleets of servers, running untrusted code securely in isolation, and porting languages into web environments efficiently.

8. ts-node – TypeScript Execution and REPL for Node.js

ts-node is a TypeScript runtime layered on top of Node.js that allows directly executing TS code without transpilation. It brings the flexibility of JavaScript to statically-typed projects.

Key Features

  • Execute TypeScript directly
  • Integrations with Node.js tooling
  • Configuration through tsconfig.json
  • Support for transpilers like Babel
  • REPL prompt to evaluate code

For teams with Node.js backends, ts-node simplifies the build pipeline by removing intermediate compilation steps. It also provides great DX with editor integration and a full REPL environment.

Ts-node fits nicely into heterogeneous codebases transitioning to TypeScript. Try it if you need to evaluate snippets of TS during development or have tricky migration paths from JS.

9. JerryScript – Lightweight Engine for Embedded Devices

JerryScript targets internet-of-things and embedded devices with an ultra compact JavaScript engine. The entire runtime fits within 100 KB of RAM and 200 KB of flash storage.

Key Features

  • Minuscule memory footprint
  • Compliance with ECMAScript 5.1 JS
  • APIs for peripheral devices
  • Portable C99 implementation

Runtimes like V8 and SpiderMonkey prioritize performance over size. Constrained devices demand the opposite trade-off focused on minimizing resource utilization.

For network firmware, smart sensors, or wearables, JerryScript enables advanced scripting capabilities without ballooning costs for hardware components. Its tiny footprint makes JS more accessible to the world of microcontrollers.

Finding the Right JavaScript Runtime

JavaScript‘s flexibility across environments is one of its greatest superpowers. Hopefully this guide provided some clarity about the spectrum of runtimes available today as well as their individual strengths.

Here are a few closing recommendations when evaluating runtimes:

  • Application type: Certain runtimes cater towards client, server or embedded use cases
  • Language flavors: Support for ES6, TypeScript or WebAssembly varies
  • Performance requirements: Memory usage, throughput and scaling capabilities differ
  • Ecosystem: Some provide more surrounding libraries/tooling than others

The JavaScript community continues innovating with new runtimes like QuickJS and Dujia. We can expect more specialization for platforms ranging from parallel computing to AR/VR devices.

Understanding runtimes unlocks the ability to execute JavaScript in places unimaginable just years ago. This flexibility remains at the heart of why JS topped StackOverflow‘s most popular language survey for the past 8 years running.

So whether bringing programming to microcontrollers, scaling web services, or crafting bespoke development environments, you now know where to turn for the right JavaScript runtime.