WebAssembly.Module

WebAssembly.Module()

Creates a new Module object.

WebAssembly.Module.customSections()

Given a Module and string, returns a copy of the contents of all custom sections in the module with the given string name.

WebAssembly.Module.exports()

Given a Module, returns an array containing descriptions of all the declared exports.

WebAssembly.Module.imports()

Given a Module, returns an array containing descriptions of all the declared imports.

The following example compiles the loaded simple.wasm byte code using the WebAssembly.compileStreaming() method and sends the resulting Module instance to a worker using postMessage().

See the index-compile.html source code or view it live.

const worker = new Worker("wasm_worker.js");

WebAssembly.compileStreaming(fetch("simple.wasm")).then((mod) =>
  worker.postMessage(mod),
);

The worker function wasm_worker.js defines an import object for the module to use. The function then sets up an event handler to receive the module from the main thread. When the module is received, we create an instance from it using the WebAssembly.instantiate() method and invoke an exported function from inside it.

const importObject = {
  my_namespace: {
    imported_func(arg) {
      console.log(arg);
    },
  },
};

onmessage = (e) => {
  console.log("module received from main thread");
  const mod = e.data;

  WebAssembly.instantiate(mod, importObject).then((instance) => {
    instance.exports.exported_func();
  });
};

• WebAssembly overview page
• WebAssembly concepts
• Using the WebAssembly JavaScript API