Scheduler

Why?

Usage

Api

Example (can run inside latest chrome)

Why?

Sometimes for smooth work (60fps) for us applications (SPA) we should manage queue and priority functions.

For this goal was created this Scheduler.

Usage

Flow is used for additional information

import Scheduler from 'Scheduler'

type Task = {
  handler: Function,
  priority?: number // some props for choose task priorty
}

getTaskWrapperFunction - This function allows us to control the execution queue tasks.

For example, a tasks can be executed synchronously, as a microtask or a macrotask.

It helps for improve performane application.

For understand

function getTaskWrapperFunction (task: Task): Function {
  const { priority } = task

  switch (true) {
    case priority === 1: {
      return // sync perform of task.handler
    }
    case priority === 2: {
      return nextTick // what is it? - http://blog.millermedeiros.com/promise-nexttick/
    }
    case priority === 3: {
      return setImmediate // pollyfill - https://github.com/YuzuJS/setImmediate
    }
    default: {
      return setTimeout
    }
  }
}

getFrameFunction - This function determines the execution time of tasks for each iteration

function getFrameFunction (tasksForFrame: Array<Task>): Function {
  var countTasks = tasksForFrame.length

  switch (true) {
    case countTasks < 30: {
      return raf
    }
    case countTasks < 100: {
      return doubleRaf
    }
    default: {
      return longRaf
    }
  }
}
// Primitive example of functions
var raf = window.requestAnimationFrame
function doubleRaf (cb) { return raf(() => raf(cb)) }
function longRaf (cb) { return setTimeout(cb, 16 * 4) }

beforeFrame - This function is performed at the beginning of each iteration

function beforeFrame (): void { (this: typeof Scheduler) }

afterFrame - This function is executed at the end of each iteration

function afterFrame (): void { (this: typeof Scheduler) }

Init and start

const instance = new Scheduler({
  getTaskWrapperFunction,
  getFrameFunction,
  beforeFrame,
  afterFrame
})

instance.start()

API

new Scheduler({ getTaskWrapperFunction?, getFrameFunction?, beforeFrame?, afterFrame? }) - Init Scheduler

getTaskWrapperFunction(task: Task): Function -

getFrameFunction(tasks: Array<Task>): Function -

beforeFrame(): void { (this: typeof Scheduler) } -

afterFrame(): void { (this: typeof Scheduler) } - description inside Usage

start() - Launch scheduler

stop() - Stops scheduler

addTask(task: Task) - Add once task

subscribeTask(task: Task) - Add task for every iteration

unsubscribeTask(task.handler: Function) - Remove task from subscribes tasks

clearTasks() - Remove all tasks from queue

clearFrameTasks() - Remove all tasks from iteration (ex. can call it inside beforeFrame)

clearSubscribesTasks() -- Remove all subscribes tasks