underline-jQuery

$(function(){
  $(window).scroll(function(){
  var windowHeight =$(window).height();
  var windowTop =$(window).scrollTop();
  $(".underline1").each(function(){
    var objectImage =$(this).offset().top;
    if(windowTop > objectImage - windowHeight*1/2){$(this).css("background-size","100% 100%")};
  });
  $(".underline2").each(function(){
    var objectImage =$(this).offset().top;
    if(windowTop > objectImage - windowHeight*1/2){$(this).css("background-size","100% 100%")};
  });
  $(".underline3").each(function(){
    var objectImage =$(this).offset().top;
    if(windowTop > objectImage - windowHeight*1/2){$(this).css("background-size","100% 100%")};
  });
});
});