Question

我正在尝试在Node.js的循环内添加延迟。我有一个数组，需要为数组的每个元素调用一个函数。要注意的是，每个这样的函数调用之间应该有30秒的间隔。这是我尝试过的-

const cprRedshift = async (page) => {
    let query = "select links from schema.table", links = [], ranks = []
    let data = await redshiftSelect(query)
    data.rows.forEach(element => {
        links.push(element.links)
    })

    let hostnames = await getDomainNames(links)

    // one way
    for(let i = 0; i < hostnames.length; i++){
            await setTimeout(async () => await checkPageRank(hostnames[i]), 30000)
    }

    // another way    
    let i = 0
    while(i < hostnames.length){
        await checkPageRank(page, hostnames[i])
        setInterval(() => ++i, 30000)
    }
}

checkPageRank是同一脚本中的一个函数，我需要针对hostnames []数组中的所有元素调用它，同时每次调用之间要保持30秒的间隔。关于如何实现这一点的任何想法将不胜感激。谢谢！

Answer 1

这是做这种事情的通用模式的简化示例：

const hostnames = ["one", "two", "three", "four", "five", "six"];

function go (index = 0) {
  // do whatever you need to do for the current index.
  console.log(hostnames[index]);
  
  // if we haven't reached the end set a timeout
  // to call this function again with the next index.
  if (hostnames.length > index + 1) {
    setTimeout(() => go(index + 1), 1000);
  }
}

// kick it off
go();

Answer 2

my previous answer的一种变体可以包括传递和使用数组本身，而不是增加一个计数器：

const hostnames = ["one", "two", "three", "four", "five", "six"];

function go ([current, ...remaining]) {
  // do whatever you need to do for the current item.
  console.log(current);
  
  // if there are items remaining, set a timeout to
  // call this function again with the remaining items
  if (remaining.length) {
    setTimeout(() => go(remaining), 1000);
  }
}

// kick it off
go(hostnames);

Answer 3

您可以使用

之类的东西

let aWait=(x)=>new Promise((resolve)=>setTimeout(resolve,x));

然后将循环重写为

 for(let i = 0; i < hostnames.length; i++){
            await checkPageRank(hostnames[i]);
            await aWait(30000);
    }

我如何在循环内的javascript中创建一个waitFor（delay）函数？

3 个答案: