Jint

Creating an engine ​

Engine owns a JavaScript realm, globals, modules, constraints, and queued work.

csharp
using Jint;

var engine = new Engine(options =>
{
    options.Strict = true;
    options.Culture = CultureInfo.GetCultureInfo("en-US");
    options.TimeZone = TimeZoneInfo.Utc;
});

Strict mode is usually preferable and can execute faster. CLR namespace access, module loading, web APIs, and Node compatibility are disabled until explicitly installed.

Reusable options ​

Configure an Options instance completely before constructing engines:

csharp
var options = new Options
{
    Strict = true
};

var first = new Engine(options);
var second = new Engine(options);

The configured instance may be shared by engines being constructed concurrently. Construction freezes the options; later setters and registrations throw. Each engine still receives its own constraint state and JavaScript realm.

Expose host values ​

csharp
var engine = new Engine()
    .SetValue("log", new Action<string>(Console.WriteLine))
    .SetValue("answer", 42);

engine.Execute("log(String(answer))");

SetValue adds a global. Exposing a CLR object grants scripts access to its public members under the interop policy.

Engine lifetime ​

An engine serves one operation at a time and is not thread-safe. Keep it assigned to one request or operation, and await any async API before reuse or disposal. A pooled engine retains globals, modules, intrinsic mutations, and caches unless the host explicitly manages them.

CaptureGlobalSnapshot and RestoreGlobalSnapshot can reset the global binding table for trusted reuse, but they are not an isolation boundary: prototype changes, reachable object graphs, CLR state, symbols, and modules survive. Use separate engines for separate trust domains. See Performance and Thread safety.