[removed] How to do something every full hour?

问题:

I want to execute some JS code every hour. But I can't use

setInterval("javascript function",60*60*1000);

because I want to do it every full hour, I mean in 1:00, in 2:00, in 3:00 and so on. I am thinking about something like

var d;
while(true) {
  d = new Date();
  if ((d.getMinutes() == '00') && (d.getSeconds() == '00')){
    // my code here
  }  
}

but it's too slow and it doesn't work well.

Thak you for any ideas

回答1:

I would find out what time it is now, figure out how long it is until the next full hour, then wait that long. So,

function doSomething() {
    var d = new Date(),
        h = new Date(d.getFullYear(), d.getMonth(), d.getDate(), d.getHours() + 1, 0, 0, 0),
        e = h - d;
    if (e > 100) { // some arbitrary time period
        window.setTimeout(doSomething, e);
    }
    // your code
}

The check for e < 100 is just to make sure you don't do setTimeout on something like 5 ms and get it a crazy loop.

回答2:

What you can do is have an interval run every minute, and check if the time is :00 before running the actual code.

回答3:

look at this one :

function to_be_executed(){
    ...
    ...
    ...
    makeInterval();
}

function makeInterval(){
    var d = new Date();
    var min = d.getMinutes();
    var sec = d.getSeconds();

    if((min == '00') && (sec == '00'))
        to_be_executed();
    else
        setTimeout(to_be_executed,(60*(60-min)+(60-sec))*1000);
}

回答4:

You could do it by clearing and setting the interval each time. It's just that first time, instead of the interval being one hour, it would be one hour minus the current minutes and seconds:

var d = new Date();
var secondsPastHour = d.getMinutes()*60 + d.getSeconds();
var intervalId = setInterval( myFn, 60*60*1000 - secondsPastHour*1000 );

function myFn() {
    // do stuff
    // ...
    clearInterval( intervalId );
    intervalId = setInterval( myFn, 60*60*1000 );
}

The only problem with this is that eventually it will probably start drifting...the solution to that would be to just do the same thing inside the function as you do when kicking it off:

var d = new Date();
var secondsPastHour = d.getMinutes()*60 + d.getSeconds();
var intervalId = setInterval( myFn, 60*60*1000 - secondsPastHour*1000 );

function myFn() {
    // do stuff
    // ...
    clearInterval( intervalId );
    var d = new Date();
    var secondsPastHour = d.getMinutes()*60 + d.getSeconds();
    intervalId = setInterval( myFn, 60*60*1000 - secondsPastHour*1000 );
}

Here's a proof of concept that updates every minute (I didn't want to wait a whole hour to test my code!): http://jsfiddle.net/dRsua/

回答5:

One simple way would be to continously run a check to detect when the hour changes:

var lastProcessedHour = -1;

setInterval(function() {
   var d = new Date();
   var currentHour = d.getHours();
   if (currentHour != lastProcessedHour) {
      // do stuff
      console.log("new hour");

      lastProcessedHour = currentHour;
   }
}, 1000);

If you run it every second like above the script will trigger one second into the new hour at the latest.

I think this method is both robust and easy to understand, and from a performance standpoint it should't really be an issue to run this simple check once every second.

回答6:

You need to run a setInterval function every minute (or every second depending on how accurate you want your timer to be) and execute your code when minutes are zero (btw get minutes returns a number between 0 and 59)..

 function myTimer() {
        var d = new Date()
        if (d.getMinutes() == 0) {
        console.log("full hour");
        }
}

 timer = setInterval(function(){myTimer()},60000)

If you do not want to have an interval running every second/minute after you established that you are on full hour you can simply trigger a new hourly interval and clear the initial one.

var myHourlyTimer = null;

     function myTimer() {
            var d = new Date()
            if (d.getMinutes() == 0) {
            console.log("full hour");
myHourlyTimer = setInterval(function(){myHourlyTimerFunction()},3600000);
clearInterval(timer)
            }
    }

 timer = setInterval(function(){myTimer()},60000)

回答7:

Was also looking for this, based on Mark's response, I wrotethis:

function callEveryFullHour() {

    var now = new Date();
    var nextHour = new Date(now.getFullYear(), now.getMonth(), now.getDate(), now.getHours() + 1, 0, 0, 0);
    var difference = nextHour - now;

    window.setTimeout(function(){

        // code goes here

        console.log("It's a full hour!")
        callEveryFullHour();

    }, difference);

}

回答8:

This is how I would go about it, expanding on the previous answer:

function callEveryFullHour(my_function) {

    var now = new Date();
    var nextHour = new Date(now.getFullYear(), now.getMonth(), now.getDate(), now.getHours() + 1, 0, 0, 0);
    var difference = nextHour - now;

    return window.setTimeout(function(){

        // run it
        my_function();

        // schedule next run
        callEveryFullHour(my_function);

    }, difference);
}

This way you can start stop any function from running on the full hour.

Usage:

let my_function = () => { // do something };
let timeout = callEveryHour(my_function);

// my_function will trigger every hour

window.clearTimeout(timeout);

// my_function will no longer trigger on the hour