task-hierarchy.js

// 代表非同步操作
let timePromise = (time)=>{return new Promise(res => setTimeout(()=> res(), time))}
let taskA = timePromise(1000)
await taskA
console.log("TaskA done")

// 此處B,C會並行
let taskB = timePromise(2000)
let taskC = timePromise(500)
await taskB
await taskC
console.log("TaskB done")
console.log("TaskC done")

// 此處 TaskD要等到 TaskB也完成才能開始
console.log("TaskD done")
console.log("TaskE done")
console.log("TaskF done")

/* 用async iife 封裝任務相依性 */
let timePromise = (time)=>{return new Promise(res => setTimeout(()=> res(), time))}

let taskA = (async ()=> { await timePromise(1000); console.log("TaskA done")})()
await taskA

let taskB = (async ()=> { await timePromise(2000); console.log("TaskB done")})()
let taskC = (async ()=> { await timePromise(500); console.log("TaskC done")})()

let taskD = (async ()=> { await taskC; console.log("TaskD done")})()
let taskE = (async ()=> { await taskB; await taskC; console.log("TaskE done")})()
let taskF = (async ()=> { await taskD; await taskE; console.log("TaskF done")})()

await taskF;