JavaScript拖拽(三):限定范围拖拽及应用自定义滚动条

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
JavaScript拖拽(三):限定范围拖拽及应用自定义滚动条_第1张图片

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!


<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。
JavaScript拖拽(三):限定范围拖拽及应用自定义滚动条_第2张图片


JavaScript拖拽(三):限定范围拖拽及应用自定义滚动条_第3张图片


<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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