♻️ extract and export a SchedulingPriority type

index.ts

@@ -4,6 +4,7 @@ export { default as yieldOrContinue } from './src/yieldOrContinue'
 // secondary
 export { default as yieldControl } from './src/yieldControl'
 export { default as isTimeToYield } from './src/isTimeToYield'
+export type { default as SchedulingPriority } from './src/SchedulingPriority'
 
 // utility
 export { default as Deferred } from './src/Deferred'

src/SchedulingPriority.ts

@@ -0,0 +1,3 @@
+type SchedulingPriority = 'user-visible' | 'background'
+
+export default SchedulingPriority

src/isTimeToYield.ts

@@ -1,5 +1,6 @@
 import state from './state'
 import hasValidContext from './hasValidContext'
+import SchedulingPriority from './SchedulingPriority'
 
 // #performance
 // calling `isTimeToYield()` thousand of times is slow. `lastCall` helps to run logic inside of
@@ -10,7 +11,7 @@ let lastResult = false
 /**
  * Determines if it's time to call `yieldControl()`.
  */
-export default function isTimeToYield(priority: 'background' | 'user-visible'): boolean {
+export default function isTimeToYield(priority: SchedulingPriority): boolean {
     if (!hasValidContext()) {
         return false
     }
@@ -34,7 +35,7 @@ export default function isTimeToYield(priority: 'background' | 'user-visible'):
     return lastResult
 }
 
-function calculateDeadline(priority: 'background' | 'user-visible'): number {
+function calculateDeadline(priority: SchedulingPriority): number {
     if (state.frameWorkStartTime === undefined) {
         // silentError()
         return -1

src/tasks.ts

@@ -1,17 +1,18 @@
 import state from './state'
 import Deferred from './Deferred'
 import { startTracking } from './tracking'
+import SchedulingPriority from './SchedulingPriority'
 
 export type Task = {
-    priority: 'background' | 'user-visible'
+    priority: SchedulingPriority
     deferred: Deferred
 }
 
 /**
  * Adds a task to the queue and returns the new task.
  * @param priority {('background' | 'user-visible')} The priority of the new task.
  */
-export function createTask(priority: 'background' | 'user-visible'): Task {
+export function createTask(priority: SchedulingPriority): Task {
     const item = { priority, deferred: new Deferred() }
     const insertIndex =
         priority === 'user-visible'

src/yieldControl.ts

@@ -4,6 +4,7 @@ import isTimeToYield from './isTimeToYield'
 import hasValidContext from './hasValidContext'
 import { createTask, nextTask, removeTask } from './tasks'
 import { cancelPromiseEscape, requestPromiseEscape } from './promiseEscape'
+import SchedulingPriority from './SchedulingPriority'
 
 let promiseEscapeId: number | undefined
 
@@ -17,7 +18,7 @@ let promiseEscapeId: number | undefined
  * resolved second.
  * @returns {Promise<void>} The promise that will be resolved when the queue
  */
-export default async function yieldControl(priority: 'user-visible' | 'background'): Promise<void> {
+export default async function yieldControl(priority: SchedulingPriority): Promise<void> {
     if (!hasValidContext()) {
         return
     }
@@ -45,7 +46,7 @@ export default async function yieldControl(priority: 'user-visible' | 'backgroun
     })
 }
 
-async function schedule(priority: 'user-visible' | 'background'): Promise<void> {
+async function schedule(priority: SchedulingPriority): Promise<void> {
     if (state.frameTimeElapsed) {
         await state.onAnimationFrame
     }

src/yieldOrContinue.ts

@@ -1,9 +1,10 @@
 import yieldControl from './yieldControl'
 import isTimeToYield from './isTimeToYield'
+import SchedulingPriority from './SchedulingPriority'
 
 // disabling ESLint otherwise `requestPromiseEscape()` in `yieldControl()` won't work
 // eslint-disable-next-line @typescript-eslint/promise-function-async
-export default function yieldOrContinue(priority: 'user-visible' | 'background'): Promise<void> {
+export default function yieldOrContinue(priority: SchedulingPriority): Promise<void> {
     if (isTimeToYield(priority)) {
         return yieldControl(priority)
     }