Question

I am trying to set an interval when some code runs but only need to do it based on the number of elements there are. Here’s a quick example:

5 total elements

Run code once every 20 seconds for each element that is found.

Can someone please give me a basic example how to do this using plain JavaScript? Everything I have tried just executes all of the code at once instead of doing one element at a time.

Answer 1

let’s suppose you’re talking about elements of an array or a DOM collection

(function() {
   var arr = [...],
       len = arr.length;


   (function doProcess() {
       if (len--) {
           /* do something with arr[len] */
           setTimeout(doProcess, 20000);
       }
   })();    
})();

Edit:
if you cannot reverse the array for any reason just use next version

(function() {
   var arr = [...],
       len = arr.length;


   (function doProcess(i) {
       if (i) {
            console.log(len - i);
           /* do something with arr[len - i] */
           setTimeout(function() { doProcess(--i); }, 20000);
       }
   })(len);    
})();