Bijou.js

Bijou.js is an open-source JavaScript runtime environment, built with Chakra in .Net/C#, and aimed at being embedded into UWP applications.

The name is inspired by our favourite pizzeria in Paris, that literally nourished this project.

How to use it

Add it to your project

1. Clone ths repository and open Bijou.js's solution file in Visual Studio 2019.
2. Compile and copy the generated binaries in your project.
3. In your project, create a new JS executor.

var engine = new BijouExecutor();

Load and run a script

Bijou.js can load and execute JS scripts using RunScriptAsync method.

// Create the engine.
var engine = new BijouExecutor();

// Run a script.
var result = await engine.RunScriptAsync(@"
                function square() { return 10 * 10; }
                square();
            ");
result = await engine.RunScriptAsync(new Uri("path/to/a/script.js"));

Call a JS function from C#

Using CallFunctionAsync method it is possible to call functions in the global JS object.

// Create the engine.
var engine = new BijouExecutor();

// First, load a script declaring a global function.
var result = await engine.RunScriptAsync(@"
                function square() { 
                    return 10 * 10; 
                }
            ");

// Then, call it.
await engine.CallFunctionAsync("square"));

Let's have more fun, let's pass some parameters to a JS function.

// Create the engine.
var engine = new BijouExecutor();

// First, load a script declaring a global function.
var result = await engine.RunScriptAsync(@"
                function multiply(a, b) {
                    return a * b; 
                }
            ");

// Then, call it passing parameters.
await engine.CallFunctionAsync("multiply", 3, 2));

This let you send data from C# to JS.

// Create the engine.
var engine = new BijouExecutor();

// First, load a script declaring a global function
var result = await engine.RunScriptAsync(@"
                function sendMessage(message) {
                    // do something with the message
                    console.log(message); 
                }
            ");

// Then, call it passing parameters
await engine.CallFunctionAsync("sendMessage", "Hello from C#"));

Sending messages from JS to C#

Bijou.js implements sendToHost API in JS, that lets sending messages from JS to C#. Calls to sendToHost trigger a OnMessageReceived event in C#. By listening to OnMessageReceived on the UWPChakraHostExecutor instance, C# code can receives calls from JS.

Let's see this in an example.

// Prepare things.
var engine = new BijouExecutor();
var messageReceived = new AutoResetEvent(false);
var timeout = TimeSpan.FromSeconds(1);
var reply = String.Empty;

// First, register to the OnMessageReceived event.
engine.OnMessageReceived += (sender, msg) => {
                    reply = msg;
                    messageReceived.Set();
                };

// Then load a cool JS function.
var result = await engine.RunScriptAsync(@"
                function coolJSFunction(message) {
                    // do something with the message
                    const reply = message + ' from JS'
                    //
                    sendToHost(reply) 
                }
            ");

// Now call it passing parameters.
await engine.CallFunctionAsync("coolJSFunction", "Hello"));

// Finally, wait for the reply.
messageReceived.WaitOne(timeout);
Debug.WriteLine(reply);

Bijou.js JavaScript API

Bijou.js is based on Chakra, and therefore is ES6-compatible.

On top of that, it implements common non-ES6 JavaScript APIs. Here's a complete list:

• Timers
  • setTimeout
  • setInterval
  • clearTimeout
  • clearInterval
• XmlHttpRequest
• console

It also provides a custom FileSystem API and encryption APIs written in C++.