jquery scroll when object appear on screen make animation

1$(window).on("scroll", function(){
2  if($(window).scrollTop() + $(window).height() - 100 >= $(".target").offset().top){
3    alert("On viewport");
4  }
5})

1body{
2  padding-top: 150vh;
3}
4
5.target{
6  background: red;
7  width: 100%;
8  height: 50px;
9  margin-bottom: 500px;
10}

1<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
2<div class="target">
3</div>