javascript事件处理模型实例说明

var EventUtil = new Object;
///
  此方法用来给特定对象添加事件，oTarget是指定对象,sEventType是事件类型，如click、keydown等，   fnHandler是事件回调函数
/
EventUtil.addEventHandler = function (oTarget, sEventType, fnHandler) {
   //firefox情况下
   if (oTarget.addEventListener) {
     oTarget.addEventListener(sEventType, fnHandler, false);
   }
   //IE下
   else if (oTarget.attachEvent) {
     oTarget.attachEvent("on" + sEventType, fnHandler);
   }
   else {
     oTarget["on" + sEventType] = fnHandler;
   }
};
/
  此方法用来移除特定对象的特定事件，oTarget是指定对象,sEventType是事件类型，如click、keydown等，fnHandler是事件回调函数
/   
EventUtil.removeEventHandler = function (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;
   }
};

/
格式化事件，因为IE和其他浏览器下获取事件的方式不同并且事件的属性也不尽相同，通过此方法提供一个一致的事件
/
EventUtil.formatEvent = function (oEvent) {
   //isIE和isWin引用到一个js文件，判断浏览器和操作系统类型
   if (isIE && isWin) {
     oEvent.charCode = (oEvent.type == "keypress") ? oEvent.keyCode : 0;
     //IE只支持冒泡，不支持捕获
     oEvent.eventPhase = 2;
     oEvent.isChar = (oEvent.charCode > 0);
     oEvent.pageX = oEvent.clientX + document.body.scrollLeft;
     oEvent.pageY = oEvent.clientY + document.body.scrollTop;
     //阻止事件的默认行为
     oEvent.preventDefault = function () {
       this.returnValue = false;
     };

      //将toElement,fromElement转化为标准的relatedTarget
     if (oEvent.type == "mouseout") {
       oEvent.relatedTarget = oEvent.toElement;
     } else if (oEvent.type == "mouseover") {
       oEvent.relatedTarget = oEvent.fromElement;
     }
     //取消冒泡   
     oEvent.sPropagation = function () {
       this.cancelBubble = true;
     };

     oEvent.target = oEvent.srcElement;
     //添加事件发生时间属性，IE没有
     oEvent.time = (new Date).getTime();
   }
   return oEvent;
};

EventUtil.getEvent = function() {
   if (window.event) {
     //格式化IE的事件
     return this.formatEvent(window.event);
   } else {
     return EventUtil.getEvent.caller.arguments[0];
   }
};

/
附带上一个判断浏览器和系统类型的js文件，通过引入一些名字显而易见的全局变量作为判断的结果，使用时需要小心变量名称冲突
/
var sUserAgent = navigator.userAgent;
var fAppVersion = parseFloat(navigator.appVersion);

function pareVersions(sVersion1, sVersion2) {

  var aVersion1 = sVersion1.split(".");
  var aVersion2 = sVersion2.split(".");
  
  if (aVersion1.length > aVersion2.length) {
    for (var i=0; i < aVersion1.length - aVersion2.length; i++) {
      aVersion2.push("0");
    }
  } else if (aVersion1.length < aVersion2.length) {
    for (var i=0; i < aVersion2.length - aVersion1.length; i++) {
      aVersion1.push("0");
    }  
  }
  
  for (var i=0; i < aVersion1.length; i++) {
 
    if (aVersion1[i] < aVersion2[i]) {
      return -1;
    } else if (aVersion1[i] > aVersion2[i]) {
      return 1;
    }  
  }
  
  return 0;

}

var isOpera = sUserAgent.indexOf("Opera") > -1;
var isMinOpera4 = isMinOpera5 = isMinOpera6 = isMinOpera7 = isMinOpera7_5 = false;

if (isOpera) {
  var fOperaVersion;
  if(navigator.appName == "Opera") {
    fOperaVersion = fAppVersion;
  } else {
    var reOperaVersion = new RegExp("Opera (//d+//.//d+)");
    reOperaVersion.test(sUserAgent);
    fOperaVersion = parseFloat(RegExp["$1"]);
  }

  isMinOpera4 = fOperaVersion >= 4;
  isMinOpera5 = fOperaVersion >= 5;
  isMinOpera6 = fOperaVersion >= 6;
  isMinOpera7 = fOperaVersion >= 7;
  isMinOpera7_5 = fOperaVersion >= 7.5;
}

var isKHTML = sUserAgent.indexOf("KHTML") > -1 
       || sUserAgent.indexOf("Konqueror") > -1 
       || sUserAgent.indexOf("AppleWebKit") > -1; 
       
var isMinSafari1 = isMinSafari1_2 = false;
var isMinKonq2_2 = isMinKonq3 = isMinKonq3_1 = isMinKonq3_2 = false;

if (isKHTML) {
  isSafari = sUserAgent.indexOf("AppleWebKit") > -1;
  isKonq = sUserAgent.indexOf("Konqueror") > -1;

  if (isSafari) {
    var reAppleWebKit = new RegExp("AppleWebKit///(//d+(?://.//d)?)");
    reAppleWebKit.test(sUserAgent);
    var fAppleWebKitVersion = parseFloat(RegExp["$1"]);

    isMinSafari1 = fAppleWebKitVersion >= 85;
    isMinSafari1_2 = fAppleWebKitVersion >= 124;
  } else if (isKonq) {

    var reKonq = new RegExp("Konqueror///(//d+(?://.//d+(?://.//d)?)?)");
    reKonq.test(sUserAgent);
    isMinKonq2_2 = pareVersions(RegExp["$1"], "2.2") >= 0;
    isMinKonq3 = pareVersions(RegExp["$1"], "3.0") >= 0;
    isMinKonq3_1 = pareVersions(RegExp["$1"], "3.1") >= 0;
    isMinKonq3_2 = pareVersions(RegExp["$1"], "3.2") >= 0;
  } 
  
}

var isIE = sUserAgent.indexOf("patible") > -1 
      && sUserAgent.indexOf("MSIE") > -1
      && !isOpera;
      
var isMinIE4 = isMinIE5 = isMinIE5_5 = isMinIE6 = false;

if (isIE) {
  var reIE = new RegExp("MSIE (//d+//.//d+);");
  reIE.test(sUserAgent);
  var fIEVersion = parseFloat(RegExp["$1"]);

  isMinIE4 = fIEVersion >= 4;
  isMinIE5 = fIEVersion >= 5;
  isMinIE5_5 = fIEVersion >= 5.5;
  isMinIE6 = fIEVersion >= 6.0;
}

var isMoz = sUserAgent.indexOf("Gecko") > -1
      && !isKHTML;

var isMinMoz1 = sMinMoz1_4 = isMinMoz1_5 = false;

if (isMoz) {
  var reMoz = new RegExp("rv:(//d+//.//d+(?://.//d+)?)");
  reMoz.test(sUserAgent);
  isMinMoz1 = pareVersions(RegExp["$1"], "1.0") >= 0;
  isMinMoz1_4 = pareVersions(RegExp["$1"], "1.4") >= 0;
  isMinMoz1_5 = pareVersions(RegExp["$1"], "1.5") >= 0;
}

var isNS4 = !isIE && !isOpera && !isMoz && !isKHTML 
      && (sUserAgent.indexOf("Mozilla") == 0) 
      && (navigator.appName == "Netscape") 
      && (fAppVersion >= 4.0 && fAppVersion < 5.0);

var isMinNS4 = isMinNS4_5 = isMinNS4_7 = isMinNS4_8 = false;

if (isNS4) {
  isMinNS4 = true;
  isMinNS4_5 = fAppVersion >= 4.5;
  isMinNS4_7 = fAppVersion >= 4.7;
  isMinNS4_8 = fAppVersion >= 4.8;
}

var isWin = (navigator.platform == "Win32") || (navigator.platform == "Windows");
var isMac = (navigator.platform == "Mac68K") || (navigator.platform == "MacPPC") 
      || (navigator.platform == "Macintosh");

var isUnix = (navigator.platform == "X11") && !isWin && !isMac;

var isWin95 = isWin98 = isWinNT4 = isWin2K = isWinME = isWinXP = false;
var isMac68K = isMacPPC = false;
var isSunOS = isMinSunOS4 = isMinSunOS5 = isMinSunOS5_5 = false;

if (isWin) {
  isWin95 = sUserAgent.indexOf("Win95") > -1 
       || sUserAgent.indexOf("Windows 95") > -1;
  isWin98 = sUserAgent.indexOf("Win98") > -1 
       || sUserAgent.indexOf("Windows 98") > -1;
  isWinME = sUserAgent.indexOf("Win 9x 4.90") > -1 
       || sUserAgent.indexOf("Windows ME") > -1;
  isWin2K = sUserAgent.indexOf("Windows NT 5.0") > -1 
       || sUserAgent.indexOf("Windows 2000") > -1;
  isWinXP = sUserAgent.indexOf("Windows NT 5.1") > -1 
       || sUserAgent.indexOf("Windows XP") > -1;
  isWinNT4 = sUserAgent.indexOf("WinNT") > -1 
       || sUserAgent.indexOf("Windows NT") > -1 
       || sUserAgent.indexOf("WinNT4.0") > -1 
       || sUserAgent.indexOf("Windows NT 4.0") > -1 
       && (!isWinME && !isWin2K && !isWinXP);
} 

if (isMac) {
  isMac68K = sUserAgent.indexOf("Mac_68000") > -1 
        || sUserAgent.indexOf("68K") > -1;
  isMacPPC = sUserAgent.indexOf("Mac_PowerPC") > -1 
        || sUserAgent.indexOf("PPC") > -1; 
}

if (isUnix) {
  isSunOS = sUserAgent.indexOf("SunOS") > -1;

  if (isSunOS) {
    var reSunOS = new RegExp("SunOS (//d+//.//d+(?://.//d+)?)");
    reSunOS.test(sUserAgent);
    isMinSunOS4 = pareVersions(RegExp["$1"], "4.0") >= 0;
    isMinSunOS5 = pareVersions(RegExp["$1"], "5.0") >= 0;
    isMinSunOS5_5 = pareVersions(RegExp["$1"], "5.5") >= 0;
  }
}