Jint

Console, diagnostics, timers, and scheduling ​

Console ​

Enabling console alone does not write to standard output. Its default ConsoleSink.Null discards records. Provide a text writer for the common case:

csharp
var engine = new Engine(options => options.UseConsole(Console.Out));
engine.Execute("console.log('hello %s', 'world')");

Derive from ConsoleSink to route ConsoleRecord values to structured logging. A record identifies the ConsoleMethod, raw arguments, log level, group depth, and trace frames. Read engine-owned JsValue arguments during the callback rather than retaining them. Console formatting does not invoke script-visible getters.

Uncaught promise rejections and errors escaping deferred callbacks use a separate DiagnosticsSink:

csharp
var engine = new Engine(options =>
    options.UseWebApis().UseDiagnostics(diagnosticsSink));

Installing a sink changes callback failure handling: without one, the exception erupts from the pump; with one, it is reported and pumping continues. Execution-limit exceptions always erupt. DiagnosticsSink.Null means continue without host output, not the same behavior as no sink.

Timers and the pump ​

Jint starts no thread or System.Threading.Timer. A timer fires on the first pump at or after its due time:

csharp
var engine = new Engine(options => options.UseWebApis());

var value = await engine.EvaluateAsync("""
    new Promise(resolve => setTimeout(() => resolve(42), 20))
    """);

Promise reactions run before due timers, and each timer gets its own microtask checkpoint. Timers, delayed scheduler tasks, idle-callback timeouts, and AbortSignal.timeout share the timer capacity; Options.WebApi.Timers.MaxActiveTimers defaults to 1,000.

Hosts that own a loop call engine.Tasks.ProcessTasks(). TimeUntilNextScheduledWork reports when to pump; WaitForScheduledWork and WaitForScheduledWorkAsync wait but never process work.

scheduler.postTask adds priority and cancellation, while scheduler.yield() resumes in a fresh task. requestIdleCallback runs only after higher-priority work; its default per-pump budget is controlled by Options.WebApi.Timers.IdleBudget.

See Thread safety before pumping from a dedicated thread.