javascript实现鼠标拖动改变层大小的方法

var theobject = null; 
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 el.offsetHeight-offset) dir += "s";
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》




　

请在边框处拖动鼠标