JavaScript 实现 div 通过八个控制点拖拽调整大小的方法

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Resize</title>
<style type="text/css">
#rRightDown,#rLeftDown,#rLeftUp,#rRightUp,#rRight,#rLeft,#rUp,#rDown{
position:absolute;background:#C00;width:6px;height:6px;z-index:5;font-size:0;}
#rLeftDown,#rRightUp{cursor:ne-resize;}
#rRightDown,#rLeftUp{cursor:nw-resize;}
#rRight,#rLeft{cursor:e-resize;}
#rUp,#rDown{cursor:n-resize;}
#rRightDown{ bottom:-3px; right:-3px;}
#rLeftDown{ bottom:-3px; left:-3px;}
#rRightUp{ top:-3px; right:-3px;}
#rLeftUp{ top:-3px; left:-3px;}
#rRight{ right:-3px; top:50%}
#rLeft{ left:-3px; top:50%}
#rUp{ top:-3px; left:50%}
#rDown{ bottom:-3px; left:50%}
</style>
</head>
<body>
<div id='ss' style="height:100px; width:100px; border:1px solid #000000; position:absolute; left:200px; top:200px;" >
<div id="rRightDown"> </div>
<div id="rLeftDown"> </div>
<div id="rRightUp"> </div>
<div id="rLeftUp"> </div>
<div id="rRight"> </div>
<div id="rLeft"> </div>
<div id="rUp"> </div>
<div id="rDown"></div>
</div>
<script>
var Sys = (function(ua){
var s = {};
s.IE = ua.match(/msie ([\\d.]+)/)?true:false;
s.Firefox = ua.match(/firefox\\/([\\d.]+)/)?true:false;
s.Chrome = ua.match(/chrome\\/([\\d.]+)/)?true:false;
s.IE6 = (s.IE&&([/MSIE (\\d)\\.0/i.exec(navigator.userAgent)][0][1] == 6))?true:false;
s.IE7 = (s.IE&&([/MSIE (\\d)\\.0/i.exec(navigator.userAgent)][0][1] == 7))?true:false;
s.IE8 = (s.IE&&([/MSIE (\\d)\\.0/i.exec(navigator.userAgent)][0][1] == 8))?true:false;
return s;
})(navigator.userAgent.toLowerCase());
var $ = function (id) { 
 return document.getElementById(id); 
};
var Css = function(e,o){ 
 for(var i in o) 
 e.style[i] = o[i]; 
};
var Extend = function(destination, source) { 
 for (var property in source) { 
 destination[property] = source[property]; 
 } 
};
var Bind = function(object, fun) { 
 var args = Array.prototype.slice.call(arguments).slice(2); 
 return function() { 
 return fun.apply(object, args); 
 } 
};
var BindAsEventListener = function(object, fun) { 
 var args = Array.prototype.slice.call(arguments).slice(2); 
 return function(event) { 
 return fun.apply(object, [event || window.event].concat(args)); 
 } 
};
var CurrentStyle = function(element){ 
 return element.currentStyle || document.defaultView.getComputedStyle(element, null); 
};
function addListener(element,e,fn){ 
 element.addEventListener?element.addEventListener(e,fn,false):element.attachEvent("on" + e,fn); 
}; 
function removeListener(element,e,fn){ 
 element.removeEventListener?element.removeEventListener(e,fn,false):element.detachEvent("on" + e,fn) 
};
var Class = function(properties){ 
 var _class = function(){return (arguments[0] !== null && this.initialize && typeof(this.initialize) == 'function') ? this.initialize.apply(this, arguments) : this;}; 
 _class.prototype = properties; 
 return _class; 
};
var Resize =new Class({ 
 initialize : function(obj){ 
 this.obj = obj; 
 this.resizeelm = null; 
 this.fun = null; //记录触发什么事件的索引 
 this.original = []; //记录开始状态的数组 
 this.width = null; 
 this.height = null; 
 this.fR = BindAsEventListener(this,this.resize); 
 this.fS = Bind(this,this.stop); 
 }, 
 set : function(elm,direction){ 
 if(!elm)return; 
 this.resizeelm = elm; 
 addListener(this.resizeelm,'mousedown',BindAsEventListener(this, this.start, this[direction])); 
 return this; 
 }, 
 start : function(e,fun){ 
 this.fun = fun; 
 this.original = [parseInt(CurrentStyle(this.obj).width),parseInt(CurrentStyle(this.obj).height),parseInt(CurrentStyle(this.obj).left),parseInt(CurrentStyle(this.obj).top)];
 this.width = (this.original[2]||0) + this.original[0]; 
 this.height = (this.original[3]||0) + this.original[1]; 
 addListener(document,"mousemove",this.fR); 
 addListener(document,'mouseup',this.fS); 
 }, 
 resize : function(e){ 
 this.fun(e); 
 Sys.IE?(this.resizeelm.onlosecapture=function(){this.fS()}):(this.resizeelm.onblur=function(){this.fS()}) 
 }, 
 stop : function(){ 
 removeListener(document, "mousemove", this.fR); 
 removeListener(document, "mousemove", this.fS); 
 window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty(); 
 }, 
 up : function(e){ 
 this.height>e.clientY?Css(this.obj,{top:e.clientY + "px",height:this.height-e.clientY + "px"}):this.turnDown(e); 
 }, 
 down : function(e){ 
 e.clientY>this.original[3]?Css(this.obj,{top:this.original[3]+'px',height:e.clientY-this.original[3]+'px'}):this.turnUp(e); 
 }, 
 left : function(e){ 
 e.clientX<this.width?Css(this.obj,{left:e.clientX +'px',width:this.width-e.clientX + "px"}):this.turnRight(e); 
 }, 
 right : function(e){ 
 e.clientX>this.original[2]?Css(this.obj,{left:this.original[2]+'px',width:e.clientX-this.original[2]+"px"}):this.turnLeft(e) ; 
 }, 
 leftUp:function(e){ 
 this.up(e);this.left(e); 
 }, 
 leftDown:function(e){ 
 this.left(e);this.down(e); 
 }, 
 rightUp:function(e){ 
 this.up(e);this.right(e); 
 }, 
 rightDown:function(e){ 
 this.right(e);this.down(e); 
 }, 
 turnDown : function(e){ 
 Css(this.obj,{top:this.height+'px',height:e.clientY - this.height + 'px'}); 
 }, 
 turnUp : function(e){ 
 Css(this.obj,{top : e.clientY +'px',height : this.original[3] - e.clientY +'px'}); 
 }, 
 turnRight : function(e){ 
 Css(this.obj,{left:this.width+'px',width:e.clientX- this.width +'px'}); 
 }, 
 turnLeft : function(e){ 
 Css(this.obj,{left:e.clientX +'px',width:this.original[2]-e.clientX+'px'}); 
 } 
}); 
window.onload = function(){ 
 new Resize($('ss')).set($('rUp'),'up').set($('rDown'),'down').set($('rLeft'),'left').set($('rRight'),'right').set($('rLeftUp'),'leftUp').set($('rLeftDown'),'leftDown').set($('rRightDown'),'rightDown').set($('rRightUp'),'rightUp');
} 
</script> 
</body> 
</html>