<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.box1{
width: 100px;
height: 100px;
background-color: red;
}
</style>
</head>
<body>
<button id="btn1">单击</button>
<button id="btn2">双击</button>
<button id="btn3">鼠标按下</button>
<button id="btn4">鼠标抬起</button>
<div id="btn5" class="box1"></div>
<script>
var btn1=document.getElementById("btn1");
var btn2=document.getElementById("btn2");
var btn3=document.getElementById("btn3");
var btn4=document.getElementById("btn4");
btn1.onclick=function(){
console.log("单击事件");
}
btn2.ondblclick=function(){
console.log("双击事件");
}
btn3.onmousedown=function(){
console.log("鼠标按下");
}
btn4.onmouseup=function(){
console.log("鼠标抬起");
}
btn5.onmousemove=function(){
console.log("鼠标移动了");
}
</script>
</body>
</html>
老师,为什么这里的btn5不需要用document.getElementById 去获取就可以使用?