let test = document.getElementById("test");
test.addEventListener("mouseover", function( event ) {
alert("mouse over test!")
, false);var target = document.querySelector(".button");
target.addEventListener("mouseover", mOver, false);
target.addEventListener("mouseout", mOut, false);
function mOver() {
target.setAttribute("style", "background-color:blue;")
}
function mOut() {
target.setAttribute("style", "background-color:green;")
} // hover in
element.addEventListener("mouseover" , function...)
// hover out
element.addEventListener("mouseout" , function...)