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WebAssembly (WASM) for High Performance Apps · Lesson

Custom JavaScript Callbacks

Design and implement custom JavaScript functions that can be called from within your WebAssembly modules.

Calling JavaScript from WASM

Sometimes, your WebAssembly (WASM) module needs to communicate back to the JavaScript environment it's running in. This is where custom JavaScript callbacks become essential!

They allow your WASM code to trigger actions or pass data back to your web page, making your applications more interactive.

Why WASM Needs Callbacks

Imagine your WASM module performs complex calculations or processes data. Once it's done, it often needs to:

  • Update the UI: Notify JavaScript to refresh a chart or display a result.
  • Access Browser APIs: Request JavaScript to use APIs WASM can't directly access, like `localStorage` or `fetch`.
  • Log Information: Send debugging messages or status updates to the browser console.
  • Handle Events: Respond to user interactions or system events managed by JavaScript.

All lessons in this course

  1. Asynchronous Operations with WASM
  2. Custom JavaScript Callbacks
  3. Error Handling & Exceptions
  4. Sharing Memory and Typed Arrays Across the JS/WASM Boundary
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