I have a u8[] array in WebAssembly code, how can I read it in regular JS? Calls to it just return me a i32.
// Load module WebAssembly.Instance
const instance = await getInstance("./build/embed.wasm");
// Try to get the array of bytes from the module
const embeddedFileBytes = Uint8Array.from(instance.fileBytes);
// write the file to disc
await writeFile("./output.text", embeddedFileBytes);
// check the hash is the same as the original file that was embedded
expect(sha1("./output.text")).toEqual(sha1("./input.text"))
The webassembly module has an export:
export const fileBytes: u8[] = [83,65,77,80,76,69,10];
WebAssembly is a low level virtual machine that only supports numeric types. More complex types, such as as strings, structs and arrays, are encoded within the WebAssembly's linear memory - which is a contiguous block of memory that both WebAssembly and JavaScript can read and write to.
The value returned by fileBytes isn't the array itself, it is instead a pointer to the location of the array in linear memory. In order to obtain the data from the array, you'll need to read it from linear memory - in much the same way as you would read a string, as described in the following question:
How can I return a JavaScript string from a WebAssembly function
If you don't want to write this 'glue' code yourself, I'd recommend looking into wasm-bindgen