JavaScript限定范围拖拽及自定义滚动条应用（3）

2019-11-19 16:34:09

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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

这里写图片描述

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范围应该在0 ~ div2.offsetWidth - div1.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/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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