Jint

Getting started ​

Requirements ​

  • .NET 8 or .NET 10
  • A Jint engine created with UseDevTools()
  • A host loop that keeps servicing the engine, or a LibraryOwned target

Install the package:

bash
dotnet add package Jint.DevTools

Create and publish a target ​

csharp
using Jint;
using Jint.DevTools;

var engine = new Engine(options => options.UseDevTools());

await using var target = new EngineTarget(engine, new EngineTargetOptions
{
    Title = "Rules engine",
    Url = "rules.js"
});

await using var server = new DevToolsServer(); // loopback, ephemeral port
server.AddTarget(target);
server.Start();

Console.WriteLine($"DevTools: {server.BrowserHttpUrl}");

With the default Port = 0, the operating system chooses a free port. After Start(), use BoundPort, BrowserHttpUrl, or BrowserWebSocketUrl to discover it.

Pump the engine ​

EngineTarget defaults to ThreadMode.HostOwned. Both script and DevTools commands must run on the engine's owning thread:

csharp
while (!stopping)
{
    target.Pump();
    engine.Tasks.WaitForScheduledWork(TimeSpan.FromMilliseconds(50));
}

engine.Tasks.ProcessTasks() may be used instead of target.Pump(). If the host does not pump, clients receive Engine is not being pumped after CommandTimeout.

Run a named script ​

Source names make scripts easier to find and breakpoint in a client:

csharp
engine.Execute(
    """
    function total(a, b) {
        return a + b;
    }
    globalThis.result = total(20, 22);
    """,
    "rules.js");

Next, connect a client. For applications without an existing engine loop, see LibraryOwned hosting.