js 0.2.3

Call JavaScript from WebAssembly
Documentation

js-wasm

This project wants to be a simple, easy to learn, technology-agnostic way to call JavaScript from WebAssembly.

Use any WebAssembly programming language out of the box:

See a demo of it working!

How It Works

Load WebAssembly like JavaScript.

<html>
    <head>
        <script src="https://cdn.jsdelivr.net/gh/richardanaya/js-wasm/js-wasm.js"></script>
        <script type="application/wasm" src="helloworld.wasm"></script>
    </head>
    <body>
        ...
    </body>
</html>

Create JavaScript functions and invoke them

Rust:

[dependencies]
js = "0.2"

let fn_log = js::register_function(
    "function(strPtr,strLen){
        console.log(this.readUtf8FromMemory(strPtr,strLen)); 
    }");

let msg = "Hello World!";

fn_log.invoke_2(msg.as_ptr() as u32, msg.len() as u32);

C/C++:

 #include "js-wasm.h"
 
JSFunction fnLog = js_register_function(
    "function(context,cstrPtr){\
        console.log(thi.getCStringFromMemory(cstrPtr));\
    }");

js_invoke_function_2(fnLog, "Hello World!");

In your JS function context this contains several functions handle most issues you'll encounter

  • readUtf8FromMemory(start,length) - Extract utf-8 text from your program's memory.
  • writeUtf8ToMemory(start,str) - Write utf-8 to a memory location you are sure it should go.
  • readCStringFromMemory(start,length) - Extract C string text from your program's memory.
  • writeCStringToMemory(start,str) - Write C string to a memory location you are sure it should go.
  • readUint8ArrayFromMemory(start) - Read a list of uint8 from a pointer to a location of a number of elements, followed by a pointer to bytes in memory.
  • storeObject(object) - Store an object in your context for later reference, get a handle you can give to WebAssembly.
  • getObject(handle) - Retreive and object from your context with a handle.
  • releaseObject(handle) - Release a stored object so it's memory can be freed.
  • module - Get access to your program so you can call methods on it.