JavaScript拖拽（三）：限定范围拖拽及应用自定义滚动条

来源：互联网发布：万德数据库怎么购买编辑：程序博客网时间：2024/05/17 01:24

两个对象：div1 和 div2，其中div1是div2的父元素，div2只能在div1的范围内拖拽

图中，红点是鼠标的位置，两个绿色箭头相减的结果就是disX，最后oEvent.clientX - disX 就是绿色箭头的部分，这个长度就是判断是否“出格”的依据，也就是这个短的绿色箭头长度范围应该在0 ~ div1.offsetWidth - div2.offsetWidth之间！

<!DOCTYPE html><html><head>    <meta charset="utf-8">    <title>客户区可见范围限制拖拽</title>    <style type="text/css">        * {            padding: 0;            margin: 0;        }        #div1 {            width: 500px;            height: 500px;            background: orange;            position: relative;            left: 100px;            top: 30px;        }        #div2 {            width: 100px;            height: 100px;            background: black;            position: absolute;            border: 1px solid blue;        }    </style></head><body>    <div id="div1">        <div id="div2"></div>    </div>    <script type="text/javascript">        var oDiv1 = document.getElementById('div1');        var oDiv2 = document.getElementById('div2');        function getStyle(obj, attr) {            if (obj.currentStyle) {                return obj.currentStyle[attr];            } else {                return getComputedStyle(obj, null)[attr];            }        }        oDiv2.onmousedown = function(ev) {            var oEvent = ev || event;            // var disX = oEvent.clientX - oDiv2.offsetLeft;            // var disY = oEvent.clientY - oDiv2.offsetTop;            var disX = oEvent.clientX - parseInt(getStyle(oDiv2, 'left'));            var disY = oEvent.clientY - parseInt(getStyle(oDiv2, 'top'));            document.onmousemove = function(ev) {                var oEvent = ev || event;                var l = oEvent.clientX - disX;                var t = oEvent.clientY - disY;                if (l < 0) {                    l = 0;                } else if (l > oDiv1.offsetWidth - /*parseInt(getStyle(oDiv2,'width'))*/oDiv2.offsetWidth) {                    l = oDiv1.offsetWidth - oDiv2.offsetWidth;                }                if (t < 0) {                    t = 0;                } else if (t > oDiv1.offsetHeight - oDiv2.offsetHeight) {                    t = oDiv1.offsetHeight - oDiv2.offsetHeight;                }                oDiv2.style.left = l + 'px';                oDiv2.style.top = t + 'px';            };            document.onmouseup = function() {                document.onmousemove = null;//如果不取消，鼠标弹起div依旧会随着鼠标移动                document.onmouseup = null;            };        };    </script></body></html>

基于上述原理，我们来做一个自定义滚动条，通过拖拽滚动条的位置来控制另一个对象的大小，比如一幅图。

这里写图片描述

<!DOCTYPE html><html><head>    <meta charset="utf-8">    <title>自定义滚动条</title>    <style type="text/css">        #div1 {            width: 600px;            height: 20px;            background: orange;            position: relative;            margin: 50px auto;        }        #div2 {            width: 20px;            height: 20px;            background: green;            position: absolute;        }        #div3 {            width: 0;            height: 0;            margin: 20px auto;        }        #div3 img {            width: 100%;            height: 100%;        }    </style></head><body>    <div id="div1">        <div id="div2"></div>    </div>    <div id="div3">        <img src="https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1495597560&di=c85bcf4f1043a0d1a432be6b3590fe05&imgtype=jpg&er=1&src=http%3A%2F%2Fstaticfile.tujia.com%2Fupload%2Finfo%2Fday_141128%2F201411281041075742.jpg">    </div>    <script type="text/javascript">        var oDiv1 = document.getElementById('div1');        var oDiv2 = document.getElementById('div2');        var oDiv3 = document.getElementById('div3');        oDiv2.onmousedown = function(ev) {            var oEvent = ev || event;            var disX = oEvent.clientX - oDiv2.offsetLeft;            document.onmousemove = function(ev) {                var oEvent = ev || event;                var l = oEvent.clientX - disX;                if (l < 0) {                    l = 0;                } else if (l > oDiv1.offsetWidth - oDiv2.offsetWidth) {                    l = oDiv1.offsetWidth - oDiv2.offsetWidth;                }                oDiv2.style.left = l + 'px';//l范围：[0,580]                //document.title = l / 580; //范围：[0,1]                var ratio = oDiv1.offsetWidth - oDiv2.offsetWidth;                var scale = l / ratio;                var w = 600 * scale;                var h = 370 * scale;                console.log(w);                oDiv3.style.cssText = ';width:' + w + 'px;height:' + h +'px;';            };            document.onmouseup = function() {                document.onmousemove = null;                document.onmouseup = null;            };        };    </script></body></html>

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