createScheduler

Stable · since 0.1.0

Constructs the dispatch scheduler used internally by the runtime. The two built-in strategies — 'microtask' and 'sync' — cover almost every real-world need; createScheduler is exposed for custom runtime composition, low-level tests, and benchmarking.

The microtask scheduler batches enqueued tasks and drains them in queueMicrotask. The sync scheduler runs tasks immediately, in the caller’s stack.

Import

import { createScheduler } from '@triggery/core';

Signature

function createScheduler(strategy: SchedulerStrategy): SchedulerImpl;

type SchedulerStrategy = 'sync' | 'microtask';

type SchedulerImpl = {
  enqueue(task: () => void): void;
  flush(): void;
};

Parameters

Param	Type	Description
`strategy`	`'sync' \| 'microtask'`	Dispatch policy.

Returns

A SchedulerImpl:

Method	Description
`enqueue(task)`	Schedule a thunk. Microtask: batches into the next microtask drain. Sync: runs immediately.
`flush()`	Drain any pending tasks now. For tests and `fireSync`. Sync scheduler keeps no queue, so its `flush` is a no-op.

Examples

Microtask batching

import { createSchedulerfunction createScheduler(strategy: SchedulerStrategy): SchedulerImpl } from '@triggery/core';

const schedconst sched: SchedulerImpl = createSchedulerfunction createScheduler(strategy: SchedulerStrategy): SchedulerImpl('microtask');
const logconst log: number[]: number[] = [];

schedconst sched: SchedulerImpl.enqueuefunction enqueue(task: Task): void(() => logconst log: number[].pushArray<number>.push(...items: number[]): numberAppends new elements to the end of an array, and returns the new length of the array.
@paramitems New elements to add to the array.(1));
schedconst sched: SchedulerImpl.enqueuefunction enqueue(task: Task): void(() => logconst log: number[].pushArray<number>.push(...items: number[]): numberAppends new elements to the end of an array, and returns the new length of the array.
@paramitems New elements to add to the array.(2));
schedconst sched: SchedulerImpl.enqueuefunction enqueue(task: Task): void(() => logconst log: number[].pushArray<number>.push(...items: number[]): numberAppends new elements to the end of an array, and returns the new length of the array.
@paramitems New elements to add to the array.(3));

// At this synchronous point, nothing has run yet.
consolevar console: Console.logConsole.log(...data: any[]): voidThe **`console.log()`** static method outputs a message to the console.

[MDN Reference](https://developer.mozilla.org/docs/Web/API/console/log_static)('queued', logconst log: number[]); // []

await Promisevar Promise: PromiseConstructorRepresents the completion of an asynchronous operation.resolvePromiseConstructor.resolve(): Promise<void> (+2 overloads)Creates a new resolved promise.
@returnsA resolved promise.(); // drain microtasks
consolevar console: Console.logConsole.log(...data: any[]): voidThe **`console.log()`** static method outputs a message to the console.

[MDN Reference](https://developer.mozilla.org/docs/Web/API/console/log_static)('drained', logconst log: number[]); // [1, 2, 3]

Synchronous dispatch

import { createSchedulerfunction createScheduler(strategy: SchedulerStrategy): SchedulerImpl } from '@triggery/core';

const schedconst sched: SchedulerImpl = createSchedulerfunction createScheduler(strategy: SchedulerStrategy): SchedulerImpl('sync');
const logconst log: number[]: number[] = [];

schedconst sched: SchedulerImpl.enqueuefunction enqueue(task: Task): void(() => logconst log: number[].pushArray<number>.push(...items: number[]): numberAppends new elements to the end of an array, and returns the new length of the array.
@paramitems New elements to add to the array.(1));
schedconst sched: SchedulerImpl.enqueuefunction enqueue(task: Task): void(() => logconst log: number[].pushArray<number>.push(...items: number[]): numberAppends new elements to the end of an array, and returns the new length of the array.
@paramitems New elements to add to the array.(2));

// Already executed inline.
consolevar console: Console.logConsole.log(...data: any[]): voidThe **`console.log()`** static method outputs a message to the console.

[MDN Reference](https://developer.mozilla.org/docs/Web/API/console/log_static)(logconst log: number[]); // [1, 2]

Error isolation in microtask mode

import { createSchedulerfunction createScheduler(strategy: SchedulerStrategy): SchedulerImpl } from '@triggery/core';

const schedconst sched: SchedulerImpl = createSchedulerfunction createScheduler(strategy: SchedulerStrategy): SchedulerImpl('microtask');

schedconst sched: SchedulerImpl.enqueuefunction enqueue(task: Task): void(() => {
  throw new Errorvar Error: ErrorConstructor
new (message?: string, options?: ErrorOptions) => Error (+1 overload)('oops');
});
schedconst sched: SchedulerImpl.enqueuefunction enqueue(task: Task): void(() => {
  consolevar console: Console.logConsole.log(...data: any[]): voidThe **`console.log()`** static method outputs a message to the console.

[MDN Reference](https://developer.mozilla.org/docs/Web/API/console/log_static)('still runs');
});

await Promisevar Promise: PromiseConstructorRepresents the completion of an asynchronous operation.resolvePromiseConstructor.resolve(): Promise<void> (+2 overloads)Creates a new resolved promise.
@returnsA resolved promise.();
// Output: "[triggery] scheduler task failed: Error: oops"
// Output: "still runs"

Notes

createRuntime The runtime picks a scheduler per trigger automatically.

createFakeScheduler Virtual-clock scheduler for tests.

Scheduling guide Microtask vs sync — when to pick which.

Concurrency strategies How async handlers interleave under each strategy.