Create a new Javascript object

var worker = JS.New("Worker", myWorkerScript);

Pass callbacks to Javascript

JS.Set("testCallback", Callback.Create<string>((strArg) => {
    Console.WriteLine($"Javascript sent: {strArg}");
    // this prints "Hello callback!"
}));

// in Javascript
testCallback('Hello callback!');

JSObject

JSObjects are wrappers around IJSInProcessReference objects that can be passed to and from Javascript and allow strongly typed access to the underlying object.

Use the extended functions of IJSInProcessObjectReference to work with Javascript objects or use the growing library of over 100 of the most common Javascript objects, including ones for Window, HTMLDocument, WebStorage (localStorage and sessionStorage), WebGL, WebRTC, and more in SpawnDev.BlazorJS.JSObjects. JSObjects are wrappers around IJSInProcessObjectReference that allow strongly typed use.

Custom JSObjects

Implement your own JSObject classes for Javascript objects not already available in the BlazorJS.JSObjects library.

Instead of this (simple but not as reusable)

var audio = JS.New("Audio", "https://some_audio_online");
audio.CallVoid("play");

You can do this...
Create a custom JSObject wrapper

[JsonConverter(typeof(JSObjectConverter<Audio>))]
public class Audio : JSObject
{
    public Audio(IJSInProcessObjectReference _ref) : base(_ref) { }
    public Audio(string url) : base(JS.New("Audio", url)) { }
    public void Play() => JSRef.CallVoid("play");
}

Then use your new object

var audio = new Audio("https://some_audio_online");
audio.Play();

SpawnDev.BlazorJS.WebWorkers

• Easily call Blazor Services in separate threads with WebWorkers and SharedWebWorkers

• Does not require SharedArrayBuffer and therefore does not require the special HTTP headers associated with using it.

• Works in Blazor WASM .Net 6, 7, and 8.

• Tested on:
  Chrome Windows - Working
  MS Edge Windows - Working
  Firefox Windows - Working
  Chrome Android - Working
  MS Edge Android - Working
  Firefox Android - Working

Firefox WebWorkers note:
Firefox does not support dynamic modules in workers, which originally made BlazorJS.WebWorkers fail in that browser. I wrote code that changes the scripts on the fly before they are loaded to workaround this limitation until Firefox finishes worker module integration. It is possible some other browsers may have this issue.

Issues can be reported here on GitHub.

Example WebWorkerService setup and usage

// Program.cs
...
using SpawnDev.BlazorJS;
using SpawnDev.BlazorJS.WebWorkers;

var builder = WebAssemblyHostBuilder.CreateDefault(args);
if (JS.IsWindow)
{
    // we can skip adding dom objects in non UI threads
    builder.RootComponents.Add<App>("#app");
    builder.RootComponents.Add<HeadOutlet>("head::after");
}
// add services
builder.Services.AddSingleton((sp) => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });
// SpawnDev.BlazorJS.WebWorkers
builder.Services.AddSingleton<WebWorkerService>();
// app specific services...
// worker services should be registered with an interface to work with WebWorker.GetService<TServiceInterface>()
builder.Services.AddSingleton<IMathsService, MathsService>();
// build 
WebAssemblyHost host = builder.Build();
// init WebWorkerService 
var workerService = host.Services.GetRequiredService<WebWorkerService>();
await workerService.InitAsync();
await host.RunAsync();

WebWorker

// Create a WebWorker
var webWorker = await workerService.GetWebWorker();

// Call GetService<ServiceInterface> on a web worker to get a proxy for the service on the web worker.
// GetService can only be called with Interface types
var workerMathService = webWorker.GetService<IMathsService>();

// Call async methods on your worker service
var result = await workerMathService.CalculatePi(piDecimalPlaces);

// Action types can be passed for progress reporting
var result = await workerMathService.CalculatePiWithActionProgress(piDecimalPlaces, new Action<int>((i) =>
{
    // the worker thread can call this method to report progress if desired
    piProgress = i;
    StateHasChanged();
}));

SharedWebWorker

Calling GetSharedWebWorker in another window with the same sharedWorkerName will return the same SharedWebWorker

// Create or get SHaredWebWorker with the provided sharedWorkerName
var sharedWebWorker = await workerService.GetSharedWebWorker("workername");

// Just like WebWorker but shared
var workerMathService = sharedWebWorker.GetService<IMathsService>();

// Call async methods on your shared worker service
var result = await workerMathService.CalculatePi(piDecimalPlaces);

Send events

// Optionally listen for event messages
worker.OnMessage += (sender, msg) =>
{
    if (msg.TargetName == "progress")
    {
        PiProgress msgData = msg.GetData<PiProgress>();
        piProgress = msgData.Progress;
        StateHasChanged();
    }
};

// From SharedWebWorker or WebWorker threads send an event to connected parents
workerService.SendEventToParents("progress", new PiProgress { Progress = piProgress });

// Or on send an event to a connected worker
webWorker.SendEvent("progress", new PiProgress { Progress = piProgress });

Worker Transferable JSObjects

Faster is better. SpawnDev WebWorkers use transferable objects by default for better performance, but it can be disabled with WorkerTransferAttribute. Setting WorkerTransfer to false will cause the property, return value, or parameter to be copied to the receiving thread instead of transferred.

Example

        public class ProcessFrameResult : IDisposable
        {
            [WorkerTransfer(false)]
            public ArrayBuffer? ArrayBuffer { get; set; }
            public byte[]? HomographyBytes { get; set; }
            public void Dispose(){
                ArrayBuffer?.Dispose();
            }
        }

        [return: WorkerTransfer(false)]
        public async Task<ProcessFrameResult?> ProcessFrame([WorkerTransfer(false)] ArrayBuffer? frameBuffer, int width, int height, int _canny0, int _canny1, double _needlePatternSize)
        {
            var ret = new ProcessFrameResult();
            // ...
            return ret;
        }

In the above example; the WorkerTransferAttribute on the return type set to false will prevent all properties of the return type from being transferred.

Transferable JSObject types

ArrayBuffer
MessagePort
ReadableStream
WritableStream
TransformStream
AudioData
ImageBitmap
VideoFrame
OffscreenCanvas
RTCDataChannel

NOTE: The above code shows quick examples. Some objects implement IDisposable, such as all JSObject, IJSInProcessObjectReference, and Callback, and need to be disposed when no longer used. Disposable objects returned from a Blazor service in a WebWorker or SharedWorker are automatically disposed after the data has been sent to the calling thread.

Support

Issues can be reported here on GitHub.

Inspired by Tewr's BlazorWorker implementation. Thank you! I wrote my implementation from scratch as I needed workers in .Net 7.
https://github.com/Tewr/BlazorWorker

BlazorJS and WebWorkers Demo
https://blazorjs.spawndev.com/

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