console 命令行工具 X clear
console
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
	<style>
		.box{
			height:200px;
			width:200px;
			background:red;
			overflow:auto;
			margin:20px;
			padding:10px;
			border:30px solid;
		}
		.box2{
			height:300px;
			width:300px;
			background:yellow;
		}
	</style>
</head>
<body>

<h1>我的第一个标题</h1>
<p>我的第一个段落。</p>
	<div class="box" id="b">
		<div class="box2">
	         1232323213211111111111111111111111111111111111111111111116666
	</div>
	</div>

</body>
	<script>
		var div = document.getElementById("b")
        //注意考虑到clientLeft存在的情况，要去除边框宽度
		var scrollBarWidth = div.offsetWidth -  div.clientWidth - div.clientLeft*2;
		var divRightBorderX = div.getBoundingClientRect().right
		var canDrag = false;
		div.addEventListener("mousedown",function(e){
			var mouseX = e.pageX;
			// 鼠标在滚动条范围内按下，不可拖拽;考虑边框宽度存在的情况，去除误差
			if(divRightBorderX - mouseX < (scrollBarWidth + div.clientLeft) && divRightBorderX - mouseX > div.clientLeft){
				canDrag = false;
				console.log("不可拖拽");
			}else{
				console.log("可拖拽");
				canDrag = true;
			}
			//console.log(scrollBarWidth,divRightBorderX,mouseX,(divRightBorderX - mouseX))
		})
		
		div.addEventListener("mouseup",function(e){
			canDrag = true;
		})
	
	</script>
</html>