TL;DR: The Microvium runtime, @microvium/runtime on npm, allows you to restore and run Microvium snapshots in a JavaScript host environment such as node.js or the browser, using a WASM build of the Microvium native engine. Why? It might seem strange to run a JavaScript engine on a JavaScript engine — why not just run the …
Microvium closures are now as small as 6 bytes on the heap, down from 12 bytes previously and compared to over 100 B in some other engines.
Closures are a good way to represent callbacks for non-blocking code. Although C doesn’t support closures, you can achieve something similar using structs on the heap, but you can get even better memory efficiency by using JavaScript running on Microvium.
Microvium’s snapshotting paradigm allows a library to generate the FFI glue code, so you don’t have to.
Microvium now has support for classes. Here are some details for the curious.
Support for closures in Microvium sets it apart from other JS engines of a similar size. Closures simplify state machines and enable functional-style code. Closures in snapshots are a new way of sharing compile-time state with the runtime program. This post goes through some examples and design details.
Microvium now has exception handling, with just 4 bytes of overhead per active try block. This post covers some of the details of the design, for those who are interested
The final output of a traditional compiler like GCC bears a family resemblance to a Microvium snapshot, but the snapshotting paradigm is both easier to use and more powerful because it allows real application code to run at build time and its state to persist until runtime.
The Microvium JavaScript engine for microcontrollers takes less than 16 kB of ROM and 64 bytes of RAM per VM while idle, making it possibly the smallest JavaScript engine to date with more language features than engines 4x its size
Single-threading with super-loops or job queues may make more efficient use of a microcontroller’s memory over time, and Microvium’s closures make single-threading easier with callback-style async code.