parcel.js/Rust: return a string

hello.rs

/*
gist is: return a ref to c_char and the length of it (via 2 functions)

C example: https://wasdk.github.io/WasmFiddle//?w590f
*/
use std::ffi::CString;
use std::os::raw::c_char;

static HELLO: &'static str = "hello from rust";

#[no_mangle]
pub fn get_hello() -> *mut c_char {
    let s = CString::new(HELLO).unwrap();
    s.into_raw()
}

#[no_mangle]
pub fn get_hello_len() -> usize {
    HELLO.len()
}

index.js

/*
based on: https://stackoverflow.com/a/47676844/653173

So you can exchange numbers and strings.
And strings could be used to transport serialized JSON,
which leads to structs (serde). So you could already cover a lot.

when build with parcel using Rust becomes that easy:
*/
import { memory, get_hello, get_hello_len } from "./hello.rs";
const offset = get_hello();
const stringBuffer = new Uint8Array(memory.buffer, offset, get_hello_len());
let str = "";
for (let i = 0; i < stringBuffer.length; i++) {
  str += String.fromCharCode(stringBuffer[i]);
}

// example: output to a div:
let div = document.getElementById('console');
div.innerText = str;