JavaScriptDOM练习之滚动条效果

html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .box {
            width: 300px;
            height: 500px;
            border: 1px solid red;
            margin: 100px;
            position: relative;
            overflow: hidden;
        }

        .content {
            padding: 5px 18px 5px 5px;
            position: absolute;
            top: 0;
            left: 0;

        }

        .scroll {
            width: 18px;
            height: 100%;
            position: absolute;
            top: 0;
            right: 0;
            background-color: #eee;
        }

        .bar {
            height: 100px;
            width: 100%;
            position: absolute;
            top: 0;
            left: 0;
            background-color: red;
            border-radius: 10px;
            cursor: pointer;
        }
    style>
head>
<body>
<div class="box" id="box">
    <div class="content" id="content">
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    div>
    <div id="scroll" class="scroll">
        <div class="bar" id="bar">div>
    div>
div>
<script src="common.js">script>
<script>
    var box = my$("box");
    var content = my$("content");
    var scroll = my$("scroll");
    var bar = my$("bar");

    //设置滚动条高度
    //滚动条的高=装滚动条的div的高*box的高/文字div的高
    var height = scroll.offsetHeight*box.offsetHeight/content.offsetHeight;
    bar.style.height = height+"px";

    bar.onmousedown = function (e) {
        var spaceY = e.clientY -bar.offsetTop;
        document.onmousemove = function (e) {
            var y = e.clientY-spaceY;
            y=y<0?0:y;
            y = y>scroll.offsetHeight-bar.offsetHeight?scroll.offsetHeight-bar.offsetHeight:y;
            bar.style.top = y+"px";


            //设置鼠标移动的时候,文字不被选中
            window.getSelection ? window.getSelection().removeAllRanges():document.selection.empty();
            //文字div的移动距离 = 轮动条的移动距离*文字div的最大移动距离/滚动条最大的移动距离
            var moveY = y*(content.offsetHeight-box.offsetHeight)/(scroll.offsetHeight-bar.offsetHeight);
            content.style.marginTop = -moveY+"px"


        }
    };
    document.onmouseup = function () {
        document.onmousemove = null;
    };
script>

body>
html>

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