每30秒运行一次ajax并显示倒数计时器

Question

I have a function that I would like to run every 30 seconds. This works fine

$(document).ready(function(){
    setInterval(function() {
        jQuery.ajax({
            type: "GET",
            url: "loaddata.php",
            dataType:"json",
            success:function(response){
                if (response) {
                    // Process
                }
                else {
                    // Process 
                }
            }

        });
    }, 30000);
});

But I am trying to figure out how I could display a countdown timer that is inline with the setInterval. In other words it should show how many seconds is left before the ajax runs, once the function runs, it should reset the timer and count down from 30 seconds again. This process would continually repeat. I found several examples of countdown timers but I have no clue how to sync it up with ajax requests and have it reset.

Any help is greatly appreciated!

Answer 1

Just run a function every second and have a counter that counts down to 0. When it hits 0, run your ajax code and reset the counter. Like so:

var count = 30;
setInterval(function() {
    count--;

    // update timer here

    if (count === 0) {
        count = 30;
        // ajax code here
    }
}, 1000);

Set the initial displayed value in your timer to 30. Then this will show 29,28,27,...,2,1,0,29,28, etc..