Making background images scale full page on all screen sizes

<script>
  var sectionId = "#lp-pom-block-8";
  //box
  var section = document.querySelector(sectionId);
  var sectionChildren = section.children;
  var otherContent = $('.lp-positioned-content').children();
  var builderHeight = $(sectionId).height();
  console.log("initial height: "+ builderHeight);
  //find initial box height
  var initHeight = builderHeight;
  
  section.style.height = "100vh";
  for(var i=0;i < sectionChildren.length; i++){
  	sectionChildren[i].style.height = "100vh";
  }
  //#lp-pom-block-8, #lp-pom-block-8 *{height:100vh;}
  var moveStuff = function(type){
//find computed box height
var finalHeight = section.clientHeight;
//find difference
var diff = finalHeight - initHeight;
for (var i=0;i<otherContent.length;i++){
  var content = $(otherContent[i]);
  var contentTop = content.position().top;
  var newTopValue = contentTop + diff;   
  content.css('top', newTopValue);
  	}
initHeight = finalHeight;
  };
	
  //Run moveStuff to adjust content on load
  moveStuff("add");  

  var resizeTimer;
  //recalculate heights on resize
  window.addEventListener("resize", function(){
clearTimeout(resizeTimer);

resizeTimer = setTimeout(function() {
  // Run code here, resizing has "stopped"
  	moveStuff();
}, 100);
  });
 
</script>