Question

问题

如果delay超过2147483648毫秒（24.8551天），该功能将立即触发。

实施例

setTimeout(function(){ console.log('hey') }, 2147483648) // this fires early
setTimeout(function(){ console.log('hey') }, 2147483647) // this works properly

我在Chrome v26和Node.js v8.21

下试用了它

Answer 1

setTimeout的上限为0x7FFFFFFF（或十进制为2147483647）

这是因为setTimeout使用32位整数来存储其延迟值，所以高于此值的任何内容都会导致问题

如果您想要在X天数之后触发超时，您可以尝试使用setInterval而不是像这样的延迟值

function setDaysTimeout(callback,days) {
    // 86400 seconds in a day
    var msInDay = 86400*1000; 

    var dayCount = 0;
    var timer = setInterval(function() {
        dayCount++;  // a day has passed

        if(dayCount == days) {
           clearInterval(timer);
           callback.apply(this,[]);
        }
    },msInDay);
}

然后你会像这样使用它

setDaysTimeout(function() {
     console.log('Four days gone');
},4); // fire after 4 days

Answer 2

由于你被限制为32位，所以只需将setTimeout包装在递归函数中，如下所示：

function setLongTimeout(callback, timeout_ms)
{

 //if we have to wait more than max time, need to recursively call this function again
 if(timeout_ms > 2147483647)
 {    //now wait until the max wait time passes then call this function again with
      //requested wait - max wait we just did, make sure and pass callback
      setTimeout(function(){ setLongTimeout(callback, (timeout_ms - 2147483647)); },
          2147483647);
 }
 else  //if we are asking to wait less than max, finally just do regular setTimeout and call callback
 {     setTimeout(callback, timeout_ms);     }
}

这不是太复杂，应该可以扩展到javascript编号的限制，即1.7976931348623157E + 10308，按这个毫秒数，我们都将死亡并消失。

为了使你能够设置setLongTimeout，你可以修改函数来接受一个通过引用传递的对象，从而将范围保留回调用函数：

function setLongTimeout(callback, timeout_ms, timeoutHandleObject)
{
 //if we have to wait more than max time, need to recursively call this function again
 if(timeout_ms > 2147483647)
 {    //now wait until the max wait time passes then call this function again with
      //requested wait - max wait we just did, make sure and pass callback
      timeoutHandleObject.timeoutHandle = setTimeout(function(){ setLongTimeout(callback, (timeout_ms - 2147483647), timeoutHandleObject); },
          2147483647);
 }
 else  //if we are asking to wait less than max, finally just do regular setTimeout and call callback
 {     timeoutHandleObject.timeoutHandle = setTimeout(callback, timeout_ms);     }
}

现在您可以调用超时，然后在需要时取消它：

var timeoutHandleObject = {};
setLongTimeout(function(){ console.log("Made it!");}, 2147483649, timeoutHandleObject);
setTimeout(function(){ clearTimeout(timeoutHandleObject.timeoutHandle); }, 5000);

如果延迟超过2147483648毫秒，则setTimeout立即触发

问题

实施例

2 个答案: