如何制作一个脚本，用POST或GET每秒轮询一次而没有滞后？

Question

I want to make a notification center for my control manager system. If I use something like this:

$(function(){
    setInterval(function(){
        $.post("url", { data: 'value' }, function(result){
            // check for updates
        });
    }, 1000);
});

the page is lagging all the time. Isn't it possible to do something like this 'on the background'? Without loading or lagging issues? If that is possible, that would be great! I tried several things but didn't have much effect.

Answer 1

you should increase your interval time to something more reasonable than 10 times/second. maybe something like once per second with a value of 1000

Answer 2

What you are referring to is called long-polling. Without knowing what your code is doing to the page, it is hard to tell what it causing lag on the page. Even so, polling every second can put a big load on your server as you scale.

You will want to increase your time interval. Something like once every 3-10 seconds won't adversely affect the user experience. People will not notice unless you are making a shared document editing or drawing application. It sounds like you are simply pushing notifications.

If you want web "real time" notifications, use WebSockets. You will still need to implement long-polling for browsers that do not support WebSockets: details here under 'Browser compatibilities' .

HTML5 Rocks has a good intro to WebSockets .

Answer 3

If you want a guaranteed interval between your calls, instead of setInterval try using a setTimeout and call the same function that has your post/get code. Something like

function myTimeout() {
  //your code for post/get
  setTimeout(myTimeout, 1000);
}

What this does is guarantee the "Previous Interval" is complete before the next call to "myTimeout" which in turn has the post. This I believe, would not be guaranteed using setInterval, which in your case calls a function making the post every 1000 milli sec no matter what. With delays, the calls may not be spaced out by the desired interval(1000 milli sec). This still does not guarantee a fixed interval between calls though(if the call/response takes longer time than the specified interval). Read more at https://developer.mozilla.org/en-US/docs/Web/API/window.setInterval under the heading "Dangerous usage"