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Modern WASM Starter

A starter template to easily create WebAssembly packages for npm using type-safe C++ code with automatic declarations. This project should take care of most of the boilerplate code required to create a modern and type-safe WebAssembly project.



Get started

Use this repo as a template to quickly start your own projects!

Build WebAssembly code

To be able to build WebAssembly code from C++ using Emscripten, you must first install and activate the emsdk. To compile the C++ code to WebAssembly, run the following command from the project's root directory.

npm install

This will create the files source/WasmModule.js and source/WasmModule.d.ts from the C++ code in the wasm directory and transpile everything into a JavaScript module in the dist directory. To build your code as wasm, add it as a CPM.cmake dependency in the CMakeLists.txt file and define the bindings in the wasmGlue.cpp source file. To update the wasm and TypeScript declarations, you can run npm run build:wasm.

Note: due to what seems to be a compiler bug, some emsdk versions seem to crash the compiler. The most recently tested working version is 1.39.20.

Run tests

The following command will build and run the test suite.

npm test

For rapid developing, tests can also be started in watch mode, which will automatically run on any code change to the TypeScript or JavaScript sources.

npm start

Fix code style

The following command will run prettier on the TypeScript and clang-format on the C++ source code.

npm run fix:style

Writing bindings

This starter uses the Glue project to create bindings and declarations. Update the wasmGlue.cpp source files to expose new classes or functions. See the Glue or EmGlue projects for documentation and examples.

Memory management

As JavaScript has no destructors, any created C++ objects must be deleted manually, or they will be leaked. To simplify this, the project introduces memory scopes that semi-automatically take care of memory management. The usage is illustrated below.

import { withGreeter } from "modern-wasm-starter";

// `withGreeter()` will run the callback asynchronously in a memory scope and return the result in a `Promise`
withGreeter(greeterModule => {
  // construct a new C++ `Greeter` instance
  const greeter = new greeterModule.Greeter("Wasm");

  // call a member function
  // any created C++ objects will be destroyed after the function exits, unless they are persisted

To see additional techniques, such as synchronous scopes or persisting and removing values outside of the scope, check out the tests or API.

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