What is WebAssembly

JavaScript has long been the cornerstone of web development, powering interactive experiences in all modern browsers. Yet, as applications demand more real-time graphics and heavy computation, JavaScript’s interpreted nature and single-threaded model can introduce performance bottlenecks.

The image illustrates performance bottlenecks in JavaScript engines, highlighting "On-the-Fly" and "Just-in-Time" processes.

JavaScript Performance Limitations

On-the-Fly Interpretation & JIT Compilation
Browsers like Chrome (V8) and Firefox (SpiderMonkey) convert JavaScript into machine code at runtime. Just-in-time (JIT) compilation speeds things up, but overhead remains for compute-heavy loops and graphics rendering.
Garbage-Collected Memory
While automatic memory management helps avoid leaks, garbage collection can cause unpredictable pauses:
let user = { name: "John" }; // Later... user = null; // triggers potential garbage collection

Single-Threaded Event Loop
async/await and Promises organize callbacks but don’t offer true parallelism:

console.log('Hi');

setTimeout(() => {
  console.log('there');
}, 5000);

console.log('JSConFEU');
// Output:
// Hi
// JSConFEU
// there   (after ~5 seconds)

Enter WebAssembly (WASM)

WebAssembly is a low-level binary format designed as a compilation target for languages like C, C++ and Rust. It runs alongside JavaScript in the browser at near-native speed, enabling performance-critical code and large codebases to execute without bulky downloads or installs.

Why Choose WebAssembly?

Feature	JavaScript	WebAssembly
Execution Model	Interpreted + JIT	Precompiled binary (near-native)
Memory Management	Garbage-collected	Linear memory with manual control
Threading	Single-threaded event loop	Potential for Web Workers & threads
Application Scope	UI, light logic	Graphics, simulations, codecs, games

WebAssembly modules interoperate seamlessly with JavaScript. You can call exported WASM functions from JS and vice versa.

Docker, Kubernetes & WebAssembly

Docker has introduced a technical preview for running WASM modules, prompting questions about the future of containers and orchestration with Kubernetes. While WASM isn’t a direct replacement for containers, it offers a lightweight sandbox for microservices and edge workloads.

A “Hello, World!” Example

Let’s compile a simple C program to both a native executable and WebAssembly module.

1. C Source Code

#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

2. Compile Natively with GCC

gcc -o wasmdemo/helloworld.exe wasmdemo/helloworld.c

Run it:

> wasmdemo/helloworld.exe
Hello, World!

3. Compile to WebAssembly with Emscripten

Install and activate the Emscripten SDK:

git clone https://github.com/emscripten-core/emsdk.git
cd emsdk
./emsdk install latest
./emsdk activate latest
source ./emsdk_env.sh    # On Windows: emsdk_env.bat

Ensure your browser supports WebAssembly threads if you plan to use shared memory and parallelism.

Compile the C code to WASM:

emcc wasmdemo/helloworld.c -o wasmdemo/helloworld.html

This generates three files:

helloworld.html – Minimal HTML page to load the module
helloworld.js – JavaScript “glue” for instantiation
helloworld.wasm – The WebAssembly binary

Inspecting the Loader

Inside helloworld.js, Emscripten handles fetching and instantiating the .wasm file:

var wasmBinaryFile = 'helloworld.wasm';
if (!isDataURI(wasmBinaryFile)) {
  wasmBinaryFile = locateFile(wasmBinaryFile);
}
function getBinary(file) {
  try {
    if (file === wasmBinaryFile && wasmBinary) {
      return new Uint8Array(wasmBinary);
    }
  } catch (e) {
    console.error(e);
  }
}

4. Execute in the Browser

Open helloworld.html in any modern browser. You should see:

Hello, World!

Congratulations! You’ve just compiled C to WebAssembly and run it alongside JavaScript—unlocking high-performance web applications for graphics, games, and more.

Introduction

Introduction to WebAssembly (WASM)

WebAssembly Core Concepts

Getting Started with WebAssembly

Compiling to WebAssembly

Future: WebAssembly in Cloud

Community & Resources

What is WebAssembly

JavaScript Performance Limitations

Enter WebAssembly (WASM)

Why Choose WebAssembly?

Docker, Kubernetes & WebAssembly

A “Hello, World!” Example

1. C Source Code

2. Compile Natively with GCC

3. Compile to WebAssembly with Emscripten

Inspecting the Loader

4. Execute in the Browser

References

Watch Video

​JavaScript Performance Limitations

​Enter WebAssembly (WASM)

​Why Choose WebAssembly?

​Docker, Kubernetes & WebAssembly

​A “Hello, World!” Example

​1. C Source Code

​2. Compile Natively with GCC

​3. Compile to WebAssembly with Emscripten

​Inspecting the Loader

​4. Execute in the Browser

​References

Watch Video

JavaScript Performance Limitations

Enter WebAssembly (WASM)

Why Choose WebAssembly?

Docker, Kubernetes & WebAssembly

A “Hello, World!” Example

1. C Source Code

2. Compile Natively with GCC

3. Compile to WebAssembly with Emscripten

Inspecting the Loader

4. Execute in the Browser

References