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前言
封装processTasks函数，实现以下需求
/*** 依次顺序执行一系列任务* 所有任务全部完成后可以得到每个任务的执行结果* 需要返回两个方法，start用于启动任务，pause用于暂停任务* 每个任务具有原子性，即不可中断，只能在两个任务之间中断* @param {...Function} tasks 任务列表，每个任务无参、异步*/
function processTasks(...tasks){}
实现
初步框架如下
function processTasks(...tasks) {const result = []let i = 0 // 当前任务索引let isRunning = false // 是否正在运行return {async start() {isRunning = truewhile (i < tasks.length) {result.push(await tasks[i]())i++if (!isRunning) return // 暂停}},pause() {isRunning = false},}
}
继续改造start的返回，手动控制Promise：
function processTasks(...tasks) {const result = []let i = 0 // 当前任务索引let isRunning = false // 是否正在运行let prom = null // 记录promise结果，防止二次调用start时重复执行之前的任务return {start() {return new Promise(async (resolve, reject) => {if (prom) {// 结束了prom.then(resolve, reject)return}if (isRunning) return // 正在运行，防止多次调用isRunning = truewhile (i < tasks.length) {try {result.push(await tasks[i]())} catch (err) {isRunning = falsereject(err)prom = Promise.reject(err)return // 失败终止}i++if (!isRunning && i < tasks.length - 1) return // 暂停}isRunning = truewhile (i < tasks.length) {try {result.push(await tasks[i]())} catch (err) {isRunning = falsereject(err)prom = Promise.reject(err)return // 失败终止}i++if (!isRunning && i < tasks.length - 1) return // 暂停}// 成功isRunning = falseresolve(result)prom = Promise.resolve(result)})},pause() {isRunning = false},}
}
测试
<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title><script src="./aa.js"></script>
</head><body><button id="start">开始任务</button><button id="pause">暂停任务</button><script>const tasks = []for (let i = 0; i < 5; i++) {tasks.push(() => new Promise(resovle => {setTimeout(() => {resovle(i)}, 2000);}))}const processor = processTasks(...tasks)start.onclick = async () => {console.log("开始任务");const results = await processor.start()console.log("任务执行完成：", results);}pause.onclick = () => {console.log("点击暂停");processor.pause()}</script>
</body></html>
使用场景
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