JavaScript 实现可缩放显示区域功能

<HTML>
<HEAD>
<TITLE>可缩放的显示区</TITLE>
<STYLE type=text/css>
BODY {
 MARGIN-TOP: 0px; FONT-SIZE: 9pt; MARGIN-LEFT: 0px; MARGIN-RIGHT: 0px; FONT-FAMILY: "宋体"
}
A {
 FONT-WEIGHT: 400; FONT-SIZE: 9pt; COLOR: black; TEXT-DECORATION: none
}
A:hover {
 FONT-WEIGHT: 400; FONT-SIZE: 9pt; COLOR: red; TEXT-DECORATION: underline
}
A:active {
 FONT: 9pt "宋体"; CURSOR: hand; COLOR: #ff0033
}
.STYLE1 {font-family: "华文彩云", "华文仿宋", "华文细黑", "华文新魏", "华文行楷", "华文中宋", "新宋体", "幼圆"}
.STYLE2 {
 font-family: "方正姚体";
 font-weight: bold;
}
</STYLE>
<META http-equiv=Content-Type content="text/html; charset=gb2312">
</HEAD>
<BODY bgColor=#fef4d9>
<CENTER>
 <span class="STYLE1"><FONT color=black size=16>可缩放的显示区</FONT></span>
</CENTER><BR>
<CENTER>
<TABLE borderColor=#00FF00 border=5 borderlight="green">
 <TBODY>
 <TR>
 <TD align=left>
 <STYLE>UNKNOWN {
 box-sizing: border-box; moz-box-sizing: border-box
}
#testDiv {
 BORDER-RIGHT: white 2px outset; PADDING-RIGHT: 2px; BACKGROUND-POSITION: 0% 50%; BORDER-TOP: white 2px outset; PADDING-LEFT: 2px; Z-INDEX: 2; BACKGROUND-ATTACHMENT: scroll; LEFT: 30px; PADDING-BOTTOM: 2px; MARGIN: 0px; OVERFLOW: hidden; BORDER-LEFT: white 2px outset; WIDTH: 500px; COLOR: #3969a5; PADDING-TOP: 2px; BORDER-BOTTOM: white 2px outset; BACKGROUND-REPEAT: repeat; HEIGHT: 300px; BACKGROUND-COLOR: buttonface
}
BODY {
 FONT-SIZE: 9pt; FONT-FAMILY: Verdana
}
#innerNice {
 BORDER-RIGHT: white 2px inset; PADDING-RIGHT: 8px; BACKGROUND-POSITION: 0% 50%; BORDER-TOP: white 2px inset; PADDING-LEFT: 8px; BACKGROUND-ATTACHMENT: scroll; PADDING-BOTTOM: 8px; OVERFLOW: auto; BORDER-LEFT: white 2px inset; WIDTH: 100%; COLOR: #3969a5; PADDING-TOP: 8px; BORDER-BOTTOM: white 2px inset; BACKGROUND-REPEAT: repeat; HEIGHT: 100%; BACKGROUND-COLOR: white
}
</STYLE>
 <DIV class=resizeMe id=testDiv>
 <DIV id=innerNice>
 <P align=center>　</P>
 <P align=center>请在边框处拖动鼠标</P>
 <P>　</P>
 <P>　</P>
 <P>　</P></DIV></DIV>
 <SCRIPT language=javascript>
var theobject = null; //This gets a value as soon as a resize start
function resizeObject() {
 this.el = null; //pointer to the object
 this.dir = ""; //type of current resize (n, s, e, w, ne, nw, se, sw)
 this.grabx = null; //Some useful values
 this.graby = null;
 this.width = null;
 this.height = null;
 this.left = null;
 this.top = null;
}
function getDirection(el) {
 var xPos, yPos, offset, dir;
 dir = "";
 xPos = window.event.offsetX;
 yPos = window.event.offsetY;
 offset = 8; //The distance from the edge in pixels
 if (yPos<offset) dir += "n";
 else if (yPos > el.offsetHeight-offset) dir += "s";
 if (xPos<offset) dir += "w";
 else if (xPos > el.offsetWidth-offset) dir += "e";
 return dir;
}
function doDown() {
 var el = getReal(event.srcElement, "className", "resizeMe");
 if (el == null) {
  theobject = null;
  return;
 }  
 dir = getDirection(el);
 if (dir == "") return;
 theobject = new resizeObject(); 
 theobject.el = el;
 theobject.dir = dir;
 theobject.grabx = window.event.clientX;
 theobject.graby = window.event.clientY;
 theobject.width = el.offsetWidth;
 theobject.height = el.offsetHeight;
 theobject.left = el.offsetLeft;
 theobject.top = el.offsetTop;
 window.event.returnValue = false;
 window.event.cancelBubble = true;
}
function doUp() {
 if (theobject != null) {
  theobject = null;
 }
}
function doMove() {
 var el, xPos, yPos, str, xMin, yMin;
 xMin = 8; //The smallest width possible
 yMin = 8; //  height
 el = getReal(event.srcElement, "className", "resizeMe");
 if (el.className == "resizeMe") {
 str = getDirection(el);
 //Fix the cursor 
  if (str == "") str = "default";
  else str += "-resize";
  el.style.cursor = str;
 }
//Dragging starts here
 if(theobject != null) {
  if (dir.indexOf("e") != -1)
   theobject.el.style.width = Math.max(xMin, theobject.width + window.event.clientX - theobject.grabx) + "px";
  if (dir.indexOf("s") != -1)
   theobject.el.style.height = Math.max(yMin, theobject.height + window.event.clientY - theobject.graby) + "px";
  if (dir.indexOf("w") != -1) {
   theobject.el.style.left = Math.min(theobject.left + window.event.clientX - theobject.grabx, theobject.left + theobject.width - xMin) + "px";
   theobject.el.style.width = Math.max(xMin, theobject.width - window.event.clientX + theobject.grabx) + "px";
  }
  if (dir.indexOf("n") != -1) {
   theobject.el.style.top = Math.min(theobject.top + window.event.clientY - theobject.graby, theobject.top + theobject.height - yMin) + "px";
   theobject.el.style.height = Math.max(yMin, theobject.height - window.event.clientY + theobject.graby) + "px";
  }
  window.event.returnValue = false;
  window.event.cancelBubble = true;
 } 
}
function getReal(el, type, value) {
 temp = el;
 while ((temp != null) && (temp.tagName != "BODY")) {
  if (eval("temp." + type) == value) {
   el = temp;
   return el;
  }
  temp = temp.parentElement;
 }
 return el;
}
document.onmousedown = doDown;
document.onmouseup = doUp;
document.onmousemove = doMove;
</SCRIPT> </TD></TR></TBODY></TABLE>
</CENTER>
</BODY>
</HTML>