如何定期检查页面状态而不刷新？

Question

I'm pretty new to (javascript) programming and I'm trying to get something automated.

There is a page that contains a countdown timer, and I want my greasemonkey script to automatically do some actions if the condition is met.

I've got this right now:

var timer = document.getElementById('timer_4975');

if (timer.innerHTML < "00:00:20"){
//Some actions
}

But this only checks the condition once when the script is loaded, when the timer goes under 00:00:20, it doesn't detect the condition is met and doesn't go to action.

Can someone guide me in the right direction?

Thanx in advance!

Answer 1

You will have to use setInterval() to execute your code more than once:

setInterval(function() {
    if(timer.innerHTML < "00:00:20") {
        //Some actions
    }
}, 5000); //Execute this function each 5 seconds.

Answer 2

You can use the setTimeout or setInterval functions to perform this task.

setInterval will perform a task regularly, which is probably more suited to what you want to achieve.

Something like:

var timer = document.getElementById('timer_4975');

var intervalHandle = setInterval(function() {
  if (timer.innerHTML < "00:00:20"){
  //Some actions
  clearInterval(intervalHandle);
  }
},1000);

would check every second (1000ms). Change the 1000 value to increase or decrease the frequency of checking... once a second is likely to be often enough.