mouseenter：当鼠标移入某元素时触发。
mouseleave：当鼠标移出某元素时触发。
mouseover：当鼠标移入某元素时触发，移入和移出其子元素时也会触发。
mouseout：当鼠标移出某元素时触发，移入和移出其子元素时也会触发。
mousemove：鼠标在某元素上移动时触发，即使在其子元素上也会触发。
mouseout、mouseover和mouseleave、mouseenter最大的区别，在于子元素连带触发。
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
.a{
width: 500px;
height: 500px;
background: aliceblue;
}
.b{
width: 200px;
height: 200px;
background: beige;
}
.c{
width: 100px;
height: 100px;
background: violet;
}
</style>
</head>
<body>
<div class="a">A
<div class="b"
onmouseenter="mouseenter()"
onmouseleave="mouseleave()"
onmouseout="mouseout()"
onmouseover="mouseover()"
onmousemove="mousemove()">B
<div class="c">C
</div>
</div>
</div>
<script>
function mouseenter(){
console.log(‘mouseenter‘)
}
function mouseleave(){
console.log(‘mouseleave‘)
}
function mouseout(){
console.log(‘mouseout‘)
}
function mouseover(){
console.log(‘mouseover‘)
}
function mousemove(){
console.log(‘mousemove‘)
}
</script>
</body>
</html>