Question

我有一个小脚本，按顺序打开和关闭3个LED。它运作良好，但我想延迟每次点亮之间的时间。

例如，我希望红色LED亮起然后关闭2秒钟，然后再转到下一个LED。

function delay() {
  return new Promise(resolve => setTimeout(resolve, 500)); //the delay between LED light ups. I'd like to add a delay between the delay.
}

async function delayedLog(item) {
  await delay();
  console.log(item);
  LED_RED.off();
  LED_GREEN.off();
  LED_YELLOW.off();
}

async function processArray(array) {
  for (const item of array) {
    if(item===1){LED_RED.on();}

    if(item===2){LED_GREEN.on();}

    if(item===3){LED_YELLOW.on();}
    await delayedLog(item);

  }
  console.log('Done!');
}

processArray([1,3,1,3,1,2,3,2,1,2,1,2,3,2,1,3]); //numbers represent LEDs. 1 is red, 2 is green and 3 is yellow.

});

Answer 1

首先，您可以修改延迟功能以接受具有延迟持续时间的参数：

function delay(duration) {
  return new Promise(resolve => setTimeout(resolve, duration));
}

由于您使用的是async / await语法，因此您可以在任何地方添加延迟：

async function delayedLog(item) {
  await delay(500);
  console.log(item);
  LED_RED.off();
  await delay(2000);
  LED_GREEN.off();
  await delay(1000);
  LED_YELLOW.off();
} // use your imagination

Answer 2

您可以使用generator和promises将数字数组处理为异步操作。

原始方法的问题在于promises只解析一次，但您需要异步处理值流。

class LED {
  constructor(number, color) {
    this.number = number
    this.color = color
  }
  on() {
    console.log(`${this.number} ${this.color} on`)
  }
  off() {
    
  }
}

const LED_RED = new LED(1, 'red')
const LED_GREEN = new LED(2, 'green')
const LED_YELLOW = new LED(3, 'yellow')

// run the given generator in sequence
function run(generator) {
  let ret
  (function iterate(val) {
    // run the next iteration of the generator
    ret = generator.next(val)
    if (!ret.done) {
      // the generator returns promises so call the promise
      ret.value.then(iterate)
    }
    else {
      console.log('Done!')
    }
  })()
}

// call the switching of lights after 2000ms
function delay(val) {
  return new Promise(
    resolve => setTimeout(() => {
      LED_RED.off()
      LED_GREEN.off()
      LED_YELLOW.off()
      switch (val) {
        case 1:   LED_RED.on(); break
        case 2:   LED_GREEN.on(); break
        default:  LED_YELLOW.on()
      }
      resolve(val)
    }, 2000)
  )
}

// generator to process the array of numbers
function *processArray(items, cb) {
  while (items.length) {
    // the execution of your program will pause here while each
    // item is processed by your delay
    yield delay(items.shift())
  }
}

run(
  processArray(
    [1,3,1,3,1,2,3,2,1,2,1,2,3,2,1,3]
  )
)

在promise中为setTimeout添加另一个延迟

2 个答案: