鼠标拖动改变DIV等网页元素的大小的实现方法

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1.初次实现

1.1 html代码

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>div change width by drag</title>
    <script src="../jQuery/jquery-1.8.3.min.js" type="text/javascript"></script>
  </head>

  <body>
    <h1>div change width by drag</h1>
    <div id="pos" style="color:red"></div>
    
    <div id="myDiv" style="border:2px solid red;width:300px;height:50px;margin-left: 100px;margin-top: 20px"></div>
  </body>
</html>

1.2 js代码

var eleLeft = $('#myDiv').offset().left;
        var isMouseDown = false;
        var borderLen = 4; //左右边框
        
        $('#myDiv').bind({
          mousedown:function(e){
            var ele = $(this);
            var rightPos = eleLeft + ele.width() + borderLen;
            if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
              isMouseDown = true;

            }
          },
      
          mousemove:function(e){
            var ele = $(this);
            var rightPos = eleLeft + ele.width() + borderLen;
            $('#pos').text("x:"+e.pageX + " eleLeft:"+eleLeft+" rightPos:"+rightPos);

            if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
              ele.css('cursor','e-resize');
            }else{
              if(!isMouseDown){
                ele.css('cursor','auto');
              }
            }
            if(isMouseDown){
              ele.width((e.pageX-eleLeft-borderLen)+'px'); //新鼠标位置-div距左-borderLen
            }
          },
          mouseup:function(e){
            isMouseDown = false;
          }
        });

1.3 结果

只能往左拖动使div宽度变小，往右拖动没有用！原因往右拖动鼠标mousemove事件无法被div捕获了。拖动时也很难停下来！所以得改进。

2.再次改进

$('#myDiv').bind({
          mousedown:function(e){
            var ele = $(this);
            var rightPos = eleLeft + ele.width() + borderLen;
            if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
              isMouseDown = true;
            }
          }
        });

        $('body').bind({
          mousemove:function(e){
            var ele = $('#myDiv');
            var rightPos = eleLeft + ele.width() + borderLen;
            $('#pos').text("x:"+e.pageX + " eleLeft:"+eleLeft+" rightPos:"+rightPos);

            if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
              ele.css('cursor','e-resize');
            }else{
              if(!isMouseDown){
                ele.css('cursor','auto');
              }
            }
            if(isMouseDown){
              ele.width((e.pageX-eleLeft-borderLen)+'px'); 
            }
          },
          mouseup:function(e){
            isMouseDown = false;
          }
        });

这次解决了上述问题，可以往右拖，并且随时可以停下来了。到这里就完成了吗？NO!

当我引入一个其他div，并且阻止mouseup事件冒泡情况怎么样呢？答案是，拖动到这个其它div上放开鼠标后无法停止下来！

<div id="otherDiv" style="border: 2px solid blue;width: 200px;height: 200px;margin-left: 400px"></div>
 

　　　　　　　　　$('#otherDiv').mouseup(function(e){
          //e.preventDefault(); //阻止默认行为
          e.stopPropagation(); //阻止事件冒泡(导致body捕获不到mouseup事件)
        });

3.完美解决

拖动停止可能受到其它元素的干扰，怎么解决？想到一些弹出层点击其它其它地方隐藏的功能，让我想到了，加一个遮罩层，让mouseup事件总是可以响应，不就搞定了嘛！

$('#myDiv').bind({
          mousedown:function(e){
            var ele = $(this);
            var rightPos = eleLeft + ele.width() + borderLen;
            if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
              isMouseDown = true;

              //创建遮罩层，防止mouseup事件被其它元素阻止冒泡，导致mouseup事件无法被body捕获，导致拖动不能停止
              var bodyWidth = $('body').width();
              var bodyHeight = $('body').height();
              $('body').append('<div id="mask" style="opacity:0.2;top:0px;left:0px;background-color:green;position:absolute;z-index:9999;width:'+bodyWidth+'px;height:'+bodyHeight+'px;"></div>');
            }
          }
        });

        $('body').bind({
          mousemove:function(e){
            var ele = $('#myDiv');
            var rightPos = eleLeft + ele.width() + borderLen;
            $('#pos').text("x:"+e.pageX + " eleLeft:"+eleLeft+" rightPos:"+rightPos);

            if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
              ele.css('cursor','e-resize');
            }else{
              if(!isMouseDown){
                ele.css('cursor','auto');
              }
            }
            if(isMouseDown){
              ele.width((e.pageX-eleLeft-borderLen)+'px'); 
            }
          },
          mouseup:function(e){
            isMouseDown = false;
            $('#mask').remove();
          }
        });

        $('#otherDiv').mouseup(function(e){
          //e.preventDefault(); //阻止默认行为
          e.stopPropagation(); //阻止事件冒泡(导致body捕获不到mouseup事件)
        });

4.完整代码和最终效果

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

    <title>div change width by drag</title>

    <script src="../jQuery/jquery-1.8.3.min.js" type="text/javascript"></script>
    
    
  </head>

  <body>
    <h1>div change width by drag</h1>
    
    <div id="pos" style="color:red"></div>
    
    
    <div id="myDiv" style="border:2px solid red;width:300px;height:50px;margin-left: 100px;margin-top: 20px"></div>

    <div id="otherDiv" style="border: 2px solid blue;width: 200px;height: 200px;margin-left: 400px"></div>
  </body>
  

  <script type="text/javascript">
      $(document).ready(function(){
        var eleLeft = $('#myDiv').offset().left;
        var isMouseDown = false;
        var borderLen = 4; //左右边框

        $('#myDiv').bind({
          mousedown:function(e){
            var ele = $(this);
            var rightPos = eleLeft + ele.width() + borderLen;
            if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
              isMouseDown = true;

              //创建遮罩层，防止mouseup事件被其它元素阻止冒泡，导致mouseup事件无法被body捕获，导致拖动不能停止
              var bodyWidth = $('body').width();
              var bodyHeight = $('body').height();
              $('body').append('<div id="mask" style="opacity:0.2;top:0px;left:0px;background-color:green;position:absolute;z-index:9999;width:'+bodyWidth+'px;height:'+bodyHeight+'px;"></div>');
            }
          }
        });

        $('body').bind({
          mousemove:function(e){
            var ele = $('#myDiv');
            var rightPos = eleLeft + ele.width() + borderLen;
            $('#pos').text("x:"+e.pageX + " eleLeft:"+eleLeft+" rightPos:"+rightPos);

            if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
              ele.css('cursor','e-resize');
            }else{
              if(!isMouseDown){
                ele.css('cursor','auto');
              }
            }
            if(isMouseDown){
              ele.width((e.pageX-eleLeft-borderLen)+'px'); 
            }
          },
          mouseup:function(e){
            isMouseDown = false;
            $('#mask').remove();
          }
        });

        $('#otherDiv').mouseup(function(e){
          //e.preventDefault(); //阻止默认行为
          e.stopPropagation(); //阻止事件冒泡(导致body捕获不到mouseup事件)
        });
      });
    </script>
</html>