本文实例讲述了JavaScript实现选择框按比例拖拉缩放的方法。分享给大家供大家参考。具体如下：
这里通过javascript实现可以像PS一样拉出一个选择框的效果。里面的很多方法都是我们值得学习的。
运行效果如下图所示：
具体代码如下：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312" /><title>JavaScript拖拉缩放效果</title></head><body><script>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); } }};</script><style type="text/css">#rRightDown,#rLeftDown,#rLeftUp,#rRightUp,#rRight,#rLeft,#rUp,#rDown{ position:absolute; background:#C00; width:7px; height:7px; 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;}#rLeftDown{left:-4px;bottom:-4px;}#rRightUp{right:-4px;top:-4px;}#rRightDown{right:-4px;bottom:-4px;background-color:#00F;}#rLeftUp{left:-4px;top:-4px;}#rRight{right:-4px;top:50%;margin-top:-4px;}#rLeft{left:-4px;top:50%;margin-top:-4px;}#rUp{top:-4px;left:50%;margin-left:-4px;}#rDown{bottom:-4px;left:50%;margin-left:-4px;}#bgDiv{width:600px; height:300px; border:10px solid #666666; position:relative;}#dragDiv{border:1px solid #000000; width:100px; height:60px; top:50px; left:50px; background:#fff;}</style><div id="bgDiv"> <div id="dragDiv"> <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></div><input id="idScale" type="button" value="设置比例" /><input id="idMin" type="button" value="设置最小范围" /><script>var rs = new Resize("dragDiv", { Max: true, mxContainer: "bgDiv" });rs.Set("rRightDown", "right-down");rs.Set("rLeftDown", "left-down");rs.Set("rRightUp", "right-up");rs.Set("rLeftUp", "left-up");rs.Set("rRight", "right");rs.Set("rLeft", "left");rs.Set("rUp", "up");rs.Set("rDown", "down");$("idScale").onclick = function(){ if(rs.Scale){ this.value = "设置比例"; rs.Scale = false; }else{ this.value = "取消比例"; rs.Ratio = 0; rs.Scale = true; }}$("idMin").onclick = function(){ if(rs.Min){ this.value = "设置最小范围"; rs.Min = false; }else{ this.value = "取消最小范围"; rs.Min = true; }}</script></body></html>希望本文所述对大家的javascript程序设计有所帮助。
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