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javascript - 在特定执行时间后返回函数

问题描述

完全清楚，如果这很重要，我会在 Node 中执行此操作。

我有一个方法可以进行一些同步调用（它们依赖于下一次调用的反馈，因此必须是同步的），而且我对环境或我正在调用的东西没有太多控制权。

无论这些调用是否完成，我都需要在设定的时间（大约 3 秒）后返回一个值。如果这些调用已完成，则脚本完成并返回该值。一种备份超时，它返回一个可接受的（如果不完整）值，而不是由于服务器执行限制而完全超时并引发错误。

我立即想到使用 a setTimeout()（clearTimeout()如果它没有被绊倒，则使用 a ）进行返回。但是，在 setTimeout 回调中返回一个值并不会结束我的脚本并返回该值，显然 - 那我该怎么办？

//"myFunction" being consumed by something I don't have control over
//Otherwise I'd just wrap the caller in a timeout
myFunction = async () => {

    var scripttimer = setTimeout(function(){
        //emergency exit - script took longer than 3 seconds
        return "I need to return a value for myFunction now"; 
    }, 3000);

    //multiple synchronous remote https calls are made
    //right here which could sometimes cause this function
    //to take more than 3 seconds, at which point the 
    //scripttimer should kill myFunction by making it return 
    //a value. That's the part that I'm asking how to do, if 
    //even possible

    if (scripttimer){
        //if we took less than 3 seconds, we don't need the backup 
        //callback in scripttimer and so we're going to kill it
        clearTimeout(scripttimer);
    }

    //best scenario return value, script took less than 3 seconds
    return "did this anyways";
}

试过了

想过做一个尝试-接住-投掷设置：

try {

    var scripttimer = setTimeout(function(){
        throw "I need to return a value for myFunction now"; 
    }, 3000);

    //wait 4 seconds maybe
    if (scripttimer){
        clearTimeout(scripttimer);
    }
    return "I don't make it out if I take too long";


} catch (e){
    return "acceptable enough";
}

......但是catch没有捕捉到它，这有点道理，因为抛出的错误超出了try-catch的范围，因为它是异步的......所以到目前为止我最好的主意。

标签： javascriptnode.jsreturnsettimeout

解决方案

如果您将httpCall功能延迟更改为小于 3 秒，那么您将获得输出为hello

如果延迟httpCall超过 3 秒，那么您将获得输出为bye

// Your Http Call Here which may take 3 seconds or more. eg.5 seconds


function httpCall(){
  return new Promise((resolve,reject)=>{
    setTimeout(function(){
        resolve("hello")
    },5000)
  });
}

// your main function where you will be calling sync functions
function operation(){
  return new Promise((resolve,reject)=>{
    const timeoutID = setTimeout(function(){
        resolve("bye")
    },3000)
    httpCall().then(result=>{
       clearTimeout(timeoutID)
       resolve(result)
    })
  });
}

// This is how you should call
operation().then((result)=>console.log(result))

在这里检查执行

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