Meziantou.Framework

Scripting

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The library never runs scripts by itself. Give a script engine to a browsing context, and the pages run their scripts as in a browser: the script elements, the modules, the event handlers, the timers, the javascript: URLs, the workers. The Meziantou.Framework.WebPlatform.JavaScript package provides the engine, based on Meziantou.Framework.JavaScriptEngine, an ECMAScript engine written in .NET.

dotnet package add Meziantou.Framework.WebPlatform.JavaScript
using var engine = new JavaScriptScriptEngine(new JavaScriptScriptEngineOptions
{
    Timeout = TimeSpan.FromSeconds(5), // per script or callback
});

using var context = new BrowsingContext(new BrowsingContextOptions
{
    ScriptEngine = engine,
    DocumentLoader = DocumentLoader.Create(), // optional: external scripts, modules, fetch, XMLHttpRequest, WebSocket, EventSource...
    UnhandledScriptError = (_, error) => Console.Error.WriteLine(error),
    ConsoleMessage = (_, message) => Console.WriteLine(message.Text), // console.log(), console.count()...
});

var document = await context.NavigateAsync("https://example.com/", _ => """
    <title>Example</title>
    <ul id=list></ul>
    <script>
      setTimeout(() => document.getElementById('list').innerHTML = '<li>a<li>b', 100);
    </script>
    """);

// Run the tasks and the timers until there is nothing left
do { await context.EventLoop.RunUntilIdleAsync(); } while (await context.EventLoop.WaitForNextTimerAsync());

Assert.Equal("<li>a</li><li>b</li>", document.GetElementById("list")!.InnerHtml);

// Evaluate code in the realm of a window
var title = engine.Evaluate(context.Window, "document.title");
Assert.Equal("Example", title.AsString());

Without a script engine

Without an engine, the scripts are never fetched or run, the event handler attributes (onclick="...") have no effect, and the javascript: URLs are ignored. The DOM, the styles and the layout work the same: a page without scripts is often all you need to read server-rendered HTML.

What the scripts can use

The scripts see the DOM and the web APIs implemented by the library, through the bindings of the browsers: the DOM and the events, fetch() and XMLHttpRequest (with a document loader), the timers, the storage, the module scripts and the import maps, the workers, the custom elements, the canvases (with a rendering backend), Web Crypto, the streams, and WebAssembly (with a WebAssembly runtime). The scripts have no access to .NET: they only see what a page sees in a browser, and the functions that you add.

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