JavaScript实现选择框按比例拖拉缩放的方法_javascript技巧

var isIE = (document.all) ? true : false;
var $ = function (id) {
 return "string" == typeof id ? document.getElementById(id) : id;
};
var Class = {
 create: function() {
 return function() { this.initialize.apply(this, arguments); }
 }
}
var Extend = function(destination, source) {
 for (var property in source) {
 destination[property] = source[property];
 }
}
var Bind = function(object, fun) {
 return function() {
 return fun.apply(object, arguments);
 }
}
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 addEventHandler(oTarget, sEventType, fnHandler) {
 if (oTarget.addEventListener) {
 oTarget.addEventListener(sEventType, fnHandler, false);
 } else if (oTarget.attachEvent) {
 oTarget.attachEvent("on" + sEventType, fnHandler);
 } else {
 oTarget["on" + sEventType] = fnHandler;
 }
};
function removeEventHandler(oTarget, sEventType, fnHandler) {
 if (oTarget.removeEventListener) {
 oTarget.removeEventListener(sEventType, fnHandler, false);
 } else if (oTarget.detachEvent) {
 oTarget.detachEvent("on" + sEventType, fnHandler);
 } else { 
 oTarget["on" + sEventType] = null;
 }
};
//缩放程序
var Resize = Class.create();
Resize.prototype = {
//缩放对象
initialize: function(obj, options) {
 this._obj = $(obj);//缩放对象 
 this._styleWidth = this._styleHeight = this._styleLeft = this._styleTop = 0;//样式参数
 this._sideRight = this._sideDown = this._sideLeft = this._sideUp = 0;//坐标参数
 this._fixLeft = this._fixTop = 0;//定位参数
 this._scaleLeft = this._scaleTop = 0;//定位坐标
 this._mxSet = function(){};//范围设置程序
 this._mxRightWidth = this._mxDownHeight = this._mxUpHeight = this._mxLeftWidth = 0;//范围参数
 this._mxScaleWidth = this._mxScaleHeight = 0;//比例范围参数
 this._fun = function(){};//缩放执行程序
 //获取边框宽度
 var _style = CurrentStyle(this._obj);
 this._borderX = (parseInt(_style.borderLeftWidth) || 0) + (parseInt(_style.borderRightWidth) || 0);
 this._borderY = (parseInt(_style.borderTopWidth) || 0) + (parseInt(_style.borderBottomWidth) || 0);
 //事件对象(用于绑定移除事件)
 this._fR = BindAsEventListener(this, this.Resize);
 this._fS = Bind(this, this.Stop);
 this.SetOptions(options);
 //范围限制
 this.Max = !!this.options.Max;
 this._mxContainer = $(this.options.mxContainer) || null;
 this.mxLeft = Math.round(this.options.mxLeft);
 this.mxRight = Math.round(this.options.mxRight);
 this.mxTop = Math.round(this.options.mxTop);
 this.mxBottom = Math.round(this.options.mxBottom);
 //宽高限制
 this.Min = !!this.options.Min;
 this.minWidth = Math.round(this.options.minWidth);
 this.minHeight = Math.round(this.options.minHeight);
 //按比例缩放
 this.Scale = !!this.options.Scale;
 this.Ratio = Math.max(this.options.Ratio, 0);
 this.onResize = this.options.onResize;
 this._obj.style.position = "absolute";
 !this._mxContainer || CurrentStyle(this._mxContainer).position == "relative" || (this._mxContainer.style.position = "relative");
 },
 //设置默认属性
 SetOptions: function(options) {
 this.options = {//默认值
 Max: false,//是否设置范围限制(为true时下面mx参数有用)
 mxContainer:"",//指定限制在容器内
 mxLeft: 0,//左边限制
 mxRight: 9999,//右边限制
 mxTop: 0,//上边限制
 mxBottom: 9999,//下边限制
 Min: false,//是否最小宽高限制(为true时下面min参数有用)
 minWidth: 50,//最小宽度
 minHeight: 50,//最小高度
 Scale: false,//是否按比例缩放
 Ratio: 0,//缩放比例(宽/高)
 onResize: function(){}//缩放时执行
 };
 Extend(this.options, options || {});
 },
 //设置触发对象
 Set: function(resize, side) {
 var resize = $(resize), fun;
 if(!resize) return;
 //根据方向设置
 switch (side.toLowerCase()) {
 case "up" :
 fun = this.Up;
 break;
 case "down" :
 fun = this.Down;
 break;
 case "left" :
 fun = this.Left;
 break;
 case "right" :
 fun = this.Right;
 break;
 case "left-up" :
 fun = this.LeftUp;
 break;
 case "right-up" :
 fun = this.RightUp;
 break;
 case "left-down" :
 fun = this.LeftDown;
 break;
 case "right-down" :
 default :
 fun = this.RightDown;
 };
 //设置触发对象
 addEventHandler(resize, "mousedown", BindAsEventListener(this, this.Start, fun));
 },
 //准备缩放
 Start: function(e, fun, touch) { 
 //防止冒泡(跟拖放配合时设置)
 e.stopPropagation ? e.stopPropagation() : (e.cancelBubble = true);
 //设置执行程序
 this._fun = fun;
 //样式参数值
 this._styleWidth = this._obj.clientWidth;
 this._styleHeight = this._obj.clientHeight;
 this._styleLeft = this._obj.offsetLeft;
 this._styleTop = this._obj.offsetTop;
 //四条边定位坐标
 this._sideLeft = e.clientX - this._styleWidth;
 this._sideRight = e.clientX + this._styleWidth;
 this._sideUp = e.clientY - this._styleHeight;
 this._sideDown = e.clientY + this._styleHeight;
 //top和left定位参数
 this._fixLeft = this._styleLeft + this._styleWidth;
 this._fixTop = this._styleTop + this._styleHeight;
 //缩放比例
 if(this.Scale){
 //设置比例
 this.Ratio = Math.max(this.Ratio, 0) || this._styleWidth / this._styleHeight;
 //left和top的定位坐标
 this._scaleLeft = this._styleLeft + this._styleWidth / 2;
 this._scaleTop = this._styleTop + this._styleHeight / 2;
 };
 //范围限制
 if(this.Max){
 //设置范围参数
 var mxLeft = this.mxLeft, mxRight = this.mxRight, mxTop = this.mxTop, mxBottom = this.mxBottom;
 //如果设置了容器，再修正范围参数
 if(!!this._mxContainer){
 mxLeft = Math.max(mxLeft, 0);
 mxTop = Math.max(mxTop, 0);
 mxRight = Math.min(mxRight, this._mxContainer.clientWidth);
 mxBottom = Math.min(mxBottom, this._mxContainer.clientHeight);
 };
 //根据最小值再修正
 mxRight = Math.max(mxRight, mxLeft + (this.Min ? this.minWidth : 0) + this._borderX);
 mxBottom = Math.max(mxBottom, mxTop + (this.Min ? this.minHeight : 0) + this._borderY);
 //由于转向时要重新设置所以写成function形式
 this._mxSet = function(){
 this._mxRightWidth = mxRight - this._styleLeft - this._borderX;
 this._mxDownHeight = mxBottom - this._styleTop - this._borderY;
 this._mxUpHeight = Math.max(this._fixTop - mxTop, this.Min ? this.minHeight : 0);
 this._mxLeftWidth = Math.max(this._fixLeft - mxLeft, this.Min ? this.minWidth : 0);
 };
 this._mxSet();
 //有缩放比例下的范围限制
 if(this.Scale){
 this._mxScaleWidth = Math.min(this._scaleLeft - mxLeft, mxRight - this._scaleLeft - this._borderX) * 2;
 this._mxScaleHeight = Math.min(this._scaleTop - mxTop, mxBottom - this._scaleTop - this._borderY) * 2;
 };
 };
 //mousemove时缩放 mouseup时停止
 addEventHandler(document, "mousemove", this._fR);
 addEventHandler(document, "mouseup", this._fS);
 if(isIE){
 addEventHandler(this._obj, "losecapture", this._fS);
 this._obj.setCapture();
 }else{
 addEventHandler(window, "blur", this._fS);
 e.preventDefault();
 };
 },
 //缩放
 Resize: function(e) {
 //清除选择
 window.getSelection ? window.getSelection().removeAllRanges() : document.selection.empty();
 //执行缩放程序
 this._fun(e);
 //设置样式，变量必须大于等于0否则ie出错
 with(this._obj.style){
 width = this._styleWidth + "px"; height = this._styleHeight + "px";
 top = this._styleTop + "px"; left = this._styleLeft + "px";
 }
 //附加程序
 this.onResize();
 },
 //缩放程序
 //上
 Up: function(e) {
 this.RepairY(this._sideDown - e.clientY, this._mxUpHeight);
 this.RepairTop();
 this.TurnDown(this.Down);
 },
 //下
 Down: function(e) {
 this.RepairY(e.clientY - this._sideUp, this._mxDownHeight);
 this.TurnUp(this.Up);
 },
 //右
 Right: function(e) {
 this.RepairX(e.clientX - this._sideLeft, this._mxRightWidth);
 this.TurnLeft(this.Left);
 },
 //左
 Left: function(e) {
 this.RepairX(this._sideRight - e.clientX, this._mxLeftWidth);
 this.RepairLeft();
 this.TurnRight(this.Right);
 },
 //右下
 RightDown: function(e) {
 this.RepairAngle(
 e.clientX - this._sideLeft, this._mxRightWidth,
 e.clientY - this._sideUp, this._mxDownHeight
 );
 this.TurnLeft(this.LeftDown) || this.Scale || this.TurnUp(this.RightUp);
 },
 //右上
 RightUp: function(e) {
 this.RepairAngle(
 e.clientX - this._sideLeft, this._mxRightWidth,
 this._sideDown - e.clientY, this._mxUpHeight
 );
 this.RepairTop();
 this.TurnLeft(this.LeftUp) || this.Scale || this.TurnDown(this.RightDown);
 },
 //左下
 LeftDown: function(e) {
 this.RepairAngle(
 this._sideRight - e.clientX, this._mxLeftWidth,
 e.clientY - this._sideUp, this._mxDownHeight
 );
 this.RepairLeft();
 this.TurnRight(this.RightDown) || this.Scale || this.TurnUp(this.LeftUp);
 },
 //左上
 LeftUp: function(e) {
 this.RepairAngle(
 this._sideRight - e.clientX, this._mxLeftWidth,
 this._sideDown - e.clientY, this._mxUpHeight
 );
 this.RepairTop(); this.RepairLeft();
 this.TurnRight(this.RightUp) || this.Scale || this.TurnDown(this.LeftDown);
 },
 //水平方向
 RepairX: function(iWidth, mxWidth) {
 iWidth = this.RepairWidth(iWidth, mxWidth);
 if(this.Scale){
 var iHeight = this.RepairScaleHeight(iWidth);
 if(this.Max && iHeight > this._mxScaleHeight){
 iHeight = this._mxScaleHeight;
 iWidth = this.RepairScaleWidth(iHeight);
 }else if(this.Min && iHeight < this.minHeight){
 var tWidth = this.RepairScaleWidth(this.minHeight);
 if(tWidth < mxWidth){ iHeight = this.minHeight; iWidth = tWidth; }
 }
 this._styleHeight = iHeight;
 this._styleTop = this._scaleTop - iHeight / 2;
 }
 this._styleWidth = iWidth;
 },
 //垂直方向
 RepairY: function(iHeight, mxHeight) {
 iHeight = this.RepairHeight(iHeight, mxHeight);
 if(this.Scale){
 var iWidth = this.RepairScaleWidth(iHeight);
 if(this.Max && iWidth > this._mxScaleWidth){
 iWidth = this._mxScaleWidth;
 iHeight = this.RepairScaleHeight(iWidth);
 }else if(this.Min && iWidth < this.minWidth){
 var tHeight = this.RepairScaleHeight(this.minWidth);
 if(tHeight < mxHeight){ iWidth = this.minWidth; iHeight = tHeight; }
 }
 this._styleWidth = iWidth;
 this._styleLeft = this._scaleLeft - iWidth / 2;
 }
 this._styleHeight = iHeight;
 },
 //对角方向
 RepairAngle: function(iWidth, mxWidth, iHeight, mxHeight) {
 iWidth = this.RepairWidth(iWidth, mxWidth); 
 if(this.Scale){
 iHeight = this.RepairScaleHeight(iWidth);
 if(this.Max && iHeight > mxHeight){
 iHeight = mxHeight;
 iWidth = this.RepairScaleWidth(iHeight);
 }else if(this.Min && iHeight < this.minHeight){
 var tWidth = this.RepairScaleWidth(this.minHeight);
 if(tWidth < mxWidth){ iHeight = this.minHeight; iWidth = tWidth; }
 }
 }else{
 iHeight = this.RepairHeight(iHeight, mxHeight);
 }
 this._styleWidth = iWidth;
 this._styleHeight = iHeight;
 },
 //top
 RepairTop: function() {
 this._styleTop = this._fixTop - this._styleHeight;
 },
 //left
 RepairLeft: function() {
 this._styleLeft = this._fixLeft - this._styleWidth;
 },
 //height
 RepairHeight: function(iHeight, mxHeight) {
 iHeight = Math.min(this.Max ? mxHeight : iHeight, iHeight);
 iHeight = Math.max(this.Min ? this.minHeight : iHeight, iHeight, 0);
 return iHeight;
 },
 //width
 RepairWidth: function(iWidth, mxWidth) {
 iWidth = Math.min(this.Max ? mxWidth : iWidth, iWidth);
 iWidth = Math.max(this.Min ? this.minWidth : iWidth, iWidth, 0);
 return iWidth;
 },
 //比例高度
 RepairScaleHeight: function(iWidth) {
 return Math.max(Math.round((iWidth + this._borderX) / this.Ratio - this._borderY), 0);
 },
 //比例宽度
 RepairScaleWidth: function(iHeight) {
 return Math.max(Math.round((iHeight + this._borderY) * this.Ratio - this._borderX), 0);
 },
 //转向程序
 //转右
 TurnRight: function(fun) {
 if(!(this.Min || this._styleWidth)){
 this._fun = fun;
 this._sideLeft = this._sideRight;
 this.Max && this._mxSet();
 return true;
 }
 },
 //转左
 TurnLeft: function(fun) {
 if(!(this.Min || this._styleWidth)){
 this._fun = fun;
 this._sideRight = this._sideLeft;
 this._fixLeft = this._styleLeft;
 this.Max && this._mxSet();
 return true;
 }
 },
 //转上
 TurnUp: function(fun) {
 if(!(this.Min || this._styleHeight)){
 this._fun = fun;
 this._sideDown = this._sideUp;
 this._fixTop = this._styleTop;
 this.Max && this._mxSet();
 return true;
 }
 },
 //转下
 TurnDown: function(fun) {
 if(!(this.Min || this._styleHeight)){
 this._fun = fun;
 this._sideUp = this._sideDown;
 this.Max && this._mxSet();
 return true;
 }
 },
 //停止缩放
 Stop: function() {
 removeEventHandler(document, "mousemove", this._fR);
 removeEventHandler(document, "mouseup", this._fS);
 if(isIE){
 removeEventHandler(this._obj, "losecapture", this._fS);
 this._obj.releaseCapture();
 }else{
 removeEventHandler(window, "blur", this._fS);
 }
 }
};