Read Rust

Tag: wasm


We will demonstrate how to do a complete port of a web application from React+Redux written in JavaScript to WebAssembly (WASM) with Rust.

This is the second part of a blog post series. You can read the first part on our website.


Rust slowly but steadily progressing into the world of web development.

Rust is easy to get started (if you wrap your head around the ownership model) and backed by an awesome community that is ready to help.

Rust provides the first class support for the WebAssembly. Rust and WebAssembly toolchain makes it easier and faster to get started with WebAssembly.

JavaScript is easy. They enabled millions (even billions) of developers to start writing applications. The fast feedback loop while development and simple API. JavaScript provides a good performance. When optimised correctly, JavaScript may yield a better performance.

The performance that JavaScript provides is not reliable and consistent. Any optimisations to increase performance is not consistent across various JavaScript engines. This makes it difficult for developers to give a better optimised and consistent performance with JavaScript.


I've been studying WebAssembly recently, which has included porting some of my m4vga graphics demos. I started with the Rust and WebAssembly Tutorial, which has you use fancy tools like wasm-pack, wasm-bindgen, webpack, and npm to produce a Rust-powered webpage.

And that's great! But I want to know how things actually work, and those tools put a lot of code between me and the machine.

In this post, I'll show how to create a simple web graphics demo using none of those tools — just hand-written Rust, JavaScript, and HTML. There will be no libraries between our code and the platform. It's the web equivalent of bare metal programming!

The resulting WebAssembly module will be less than 300 bytes. That's about the same size as the previous paragraph.


Wasm Pack is a flexible framework in the Rust ecosystem to compile code to WebAssembly. It allows web developers to outsource their most demanding data processing tasks to some safe and high-performance Rust code. But it also provides Rust developers with an easy access to Web technologies for creating GUIs for their libraries. Elm is a fairly new language that has revolutionised the way highly interactive web pages are built. This tutorial presents a way to use Elm in conjunction with Rust to produce powerful web applications.

wasm elm

I originally wrote Sorta Secret a year ago in Rust using actix-web and deployed it, like most services we write at FP Complete, to our Kubernetes cluster. When Rust 1.39 was released with async/await support, and then Hyper 0.13 was released using that support, I decided I wanted to try rewriting against Hyper. But that's a story for another time.

After that, more out of curiosity than anything else, I decided to rewrite it as a serverless application using Cloudflare Workers, a serverless platform that supports Rust and WASM.

This post will describe my experiences doing this, what I thought worked well (and not so well), and why you may consider doing something like this yourself.


We will demonstrate how to do a complete port of a web application from React+Redux written in JavaScript to WebAssembly (WASM) with Rust. This is the first part of a blog post series.


In a project I’ve been playing around with recently, we’ve encountered the dilemma where you want to make it easy for users to write their own application logic using the system but at the same time want to keep that logic decoupled from the implementation details of whatever platform the application is running on.


Using a Rust image manipulation library via WebAssembly, service workers can manipulate images on the fly. You can see a simple example of the code here and a fully-fledged example here.


Multi-value is a proposed extension to core WebAssembly that enables functions to return many values, among other things. It is also a pre-requisite for Wasm interface types.

I’ve been adding multi-value support all over the place recently: I added multi-value support to all the various crates in the Rust and WebAssembly toolchain, so that Rust projects can compile down to Wasm code that uses multi-value features. I added multi-value support to Wasmtime, the WebAssembly runtime built on top of the Cranelift code generator, so that it can run Wasm code that uses multi-value features.

Now, as my multi-value efforts are wrapping up, it seems like a good time to reflect on the experience and write up everything that’s been required to get all this support in all these places.


Today we announce the formation of the Bytecode Alliance, a new industry partnership coming together to forge WebAssembly’s outside-the-browser future by collaborating on implementing standards and proposing new ones. Our founding members are Mozilla, Fastly, Intel, and Red Hat, and we’re looking forward to welcoming many more.


Wasmtime is a standalone wasm-only optimizing runtime for WebAssembly and WASI, using Cranelift. It runs WebAssembly code outside of the Web, and can be used both as a command-line utility or as a library embedded in a larger application.

wasm wasi

In our last adventure we looked at C++ exceptions in WebAssembly with the emscripten compiler. Now we’re taking a look at the main error handling system for another language targeting WebAssembly, Rust. Rust has a “panic”/”unwind” system similar to C++ exceptions, but it’s generally recommended against catching panics.

wasm error-handling

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