let pos = 0;

window.addEventListener("load", function(event) {
    testIt('current', 5000);
});

function testIt(_class, _speed) {
   const testPara = document.querySelectorAll('.bg_imgs');

   let i;
   for(i = 0; i < testPara.length; i++) {
       testPara[i].classList.remove(_class);
   }

   pos++;


   if(pos > testPara.length) {pos = 1;}

   testPara[pos-1].classList.add(_class);

   setTimeout(_class, _speed); }