WASM Bindings (wasm-bindgen)

Last Updated March 24, 2026

The primary environment for MDX is JavaScript. Whether you are building a static site with Next.js or a real-time collaborative editor in React, you need to parse MDX in a JavaScript thread.

To achieve native parsing speeds inside a web browser without writing slow JavaScript, we compile the Omni-Core Rust engine to WebAssembly (WASM) using wasm-bindgen.

The WASM Paradigm

WebAssembly is not a programming language; it is a binary instruction format for a stack-based virtual machine. It allows code written in languages like Rust or C++ to run in web browsers at near-native speed.

wasm-bindgen is the toolchain we use to facilitate high-level communication between Rust and JavaScript. It automatically generates the JavaScript glue code needed to load the .wasm binary, instantiate it, and call its exported functions.

When your React component calls:

import { parseMdx } from '@toaq-oss/omni-mdx/client';

const ast = parseMdx("# Hello from WASM");

You are executing pre-compiled Rust bytecode inside the browser’s WASM virtual machine.

Linear Memory & Shared Buffers

WebAssembly operates on a fundamentally different memory model than JavaScript. WASM does not have access to the JavaScript heap. Instead, it has its own, contiguous block of raw memory called Linear Memory.

This is where Omni-MDX’s architecture truly shines.

As we discussed in the Zero-Copy section, when the Rust engine finishes parsing:

1. It allocates the OCP Binary payload inside its WASM Linear Memory.
2. It returns the memory pointer (usize) and the length to JavaScript.
3. The JavaScript SDK creates a view over that exact memory segment:

// Inside the JS SDK
const buffer = new Uint8Array(wasm.memory.buffer, ptr, length);

Because JavaScript is looking directly into WASM’s RAM, we achieve true Zero-Copy data transfer. The host language can start reading the AST instructions without moving a single byte of data.

Deployment with wasm-pack

Packaging a WASM module for use in a modern web application (with tools like Webpack, Vite, or Next.js) can be complex. We simplify this process using wasm-pack.

In our CI/CD pipeline, wasm-pack automatically:

• Compiles the Rust core to wasm32-unknown-unknown.
• Generates the TypeScript definition files (.d.ts).
• Generates the package.json for the @omni-mdx/wasm package.

For web developers, Omni-MDX feels like any other npm package. They don’t need to know Rust or configure complex WASM loaders; they just install it and profit from sub-millisecond parsing speed.