任务队列的中断和恢复

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/**
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 * 依次顺序执行一系列任务
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 * 所有任务全部完成后可以得到每个任务的执行的结果
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 * 需要返回两个方法，start 用于启动任务， pause 用于暂停任务
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 * 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
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 * @param {...Function} tasks 任务列表，每个任务无参、异步
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 */
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function processTasks(...tasks) {
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    // 任务队列
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    const tasksQueue = []
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    // 是否正在运行
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    let isRunning = false
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    // 当前执行任务索引
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    let currentIndex = 0
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    async function start() {
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        return new Promise((resolve, reject) => {
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            // 如果正在运行则直接返回
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            if (isRunning) return
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            isRunning = true
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            // 启动任务
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            while (currentIndex < tasks.length) {
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                // 执行任务
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                tasksQueue.push(tasks[currentIndex++]())
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                if (!isRunning) break
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            }
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            // 等待所有任务执行完毕
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            isRunning = false
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            resolve(tasksQueue)
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        })
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    }
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    function pause() {
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        isRunning = false
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    }
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    return {
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        start,
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        pause
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    }
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}
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const tasks = [
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  async () => {
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    console.log("task1 start");
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    await new Promise((resolve) => setTimeout(resolve, 2000));
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    console.log("task1 end");
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    return "task1 result";
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  },
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  async () => {
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    console.log("task2 start");
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    await new Promise((resolve) => setTimeout(resolve, 1000));
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    console.log("task2 end");
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    return "task2 result";
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  },
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  async () => {
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    console.log("task3 start");
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    await new Promise((resolve) => setTimeout(resolve, 3000));
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    console.log("task3 end");
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    return "task3 result";
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  },
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];
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const { start, pause } = processTasks(...tasks);
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start().then((results) => {
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  console.log(results);
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  pause();
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});

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task1 start
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task2 start
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task3 start
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[ Promise { <pending> }, Promise { <pending> }, Promise { <pending> } ]
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task2 end
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task1 end
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task3 end