Answers for "what is hover in js"

style hover js

<div id="mydiv">foo</div>

<script>
document.getElementById("mydiv").onmouseover = function() 
{
    this.style.backgroundColor = "blue";
}
</script>

js hover event

// You can use jQuery

$("p").hover(function(){
  $(this).css("background-color", "yellow");
  }, function(){
  $(this).css("background-color", "pink");
});