Web Assembly

WebAssembly is a binary format for describing a program's data and instructions. It is a new and more efficient binary format.

We create a new Uint8Array with the bytes of the WebAssembly module. This is usually the output of some compiler and not written by hand.

const bytes = new Uint8Array([
  0,97,115,109,1,0,0,0,1,7,1,96,2,
  127,127,1,127,2,1,0,3,2,1,0,4,1,
  0,5,1,0,6,1,0,7,7,1,3,97,100,100,
  0,0,9,1,0,10,10,1,8,0,32,0,32,1,
  106,15,11,11,1,0,
]);

We create an interface for the WebAssembly module containing all exports.

interface WebAssemblyExports {
  add(a: number, b: number): number;
}

The WebAssembly module is a binary format for describing a program's data and instructions.

const exports = await WebAssembly.instantiate(bytes);

We get the exports from the WebAssembly module and cast it to the interface.

const functions = exports.instance.exports as unknown as WebAssemblyExports;

We call the exported function.

console.log(functions.add(1, 2)); // 3

Run this example locally using the Deno CLI:

deno run https://byexample-wwv03xf36j0g.deno.dev/webassembly.ts

Additional resources:

Web Workers Manipulating byte arrays