​​​​​​​<div class="my_img_container">
   <img src="//www.domain.com/img/20170714aksdjkasdljaldkjs--alt-My_Test_Image_Alt--title-My_Test_Image_Title--caption-CAPTIONN-HERE.jpg">
</div>


<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script>
   $(function(){
      $(".my_img_container img").each(function(){
         var src = $(this).attr('src');
         var r = src.match(/\/([^\/]+)\.[a-zA-Z]{3,4}$/);
         var substrs = r[1].split('--');
         for (var i = 0, len = substrs.length; i < len; i++) {
            var attrs = substrs[i].match(/([a-z]+)\-(.*)/i);
            if (attrs !== null) {
               console.log(attrs[2]);
               if (attrs[1] == 'alt' || attrs[1] == 'title' || attrs[1] == 'caption') {
                  $(this).attr(attrs[1],attrs[2].replace(/_/g, ' '));
               }
            }
         }
      })
   });
</script>