常用原生JS兼容性写法汇总

addHandler：function(element,type,handler){
 if(element.addEventListener){//检测是否为DOM2级方法
  element.addEventListener(type, handler, false);
 }else if (element.attachEvent){//检测是否为IE级方法
  element.attachEvent("on" + type, handler);
 } else {//检测是否为DOM0级方法
  element["on" + type] = handler;
 }
}

removeHandler：function(element, type, handler){
  if (element.removeEventListener){
   element.removeEventListener(type, handler, false);
  } else if (element.detachEvent){
   element.detachEvent("on" + type, handler);
  } else {
   element["on" + type] = null;
  }
 }

//获取事件对象的兼容性写法
 getEvent: function(event){
  return event ? event : window.event;
 },
 //获取事件对象目标的兼容性写法
 getTarget: function(event){
  return event.target || event.srcElement;
 }

preventDefault: function(event){
  if (event.preventDefault){
   event.preventDefault();
  } else {
   event.returnValue = false;
  }
 }

stopPropagation: function(event){
  if (event.stopPropagation){
   event.stopPropagation();
  } else {
   event.cancelBubble = true;
  }
 }

//mouseover和mouseout 事件才包含的获取相关元素的方法
getRelatedTarget: function(event){
 if (event.relatedTarget){
  return event.relatedTarget;
 } else if (event.toElement){
  return event.toElement;
 } else if (event.fromElement){
  return event.fromElement;
 } else {
  return null;
 }
}

getButton: function(event){
 if (document.implementation.hasFeature("MouseEvents", "2.0")){
  return event.button;
 } else {
  switch(event.button){
   case 0:
   case 1:
   case 3:
   case 5:
   case 7:
   return 0;
   case 2:
   case 6:
   return 2;
   case 4:
   return 1;
  }
 }
}

getWheelDelta: function(event){
 if (event.wheelDelta){
  return (client.engine.opera && client.engine.opera < 9.5 ?
   -event.wheelDelta : event.wheelDelta);
 } else {
  return -event.detail * 40;//firefox中的值为+3表示向上滚，-3表示向下滚
 }
}

getCharCode: function(event){
 if (typeof event.charCode == "number"){
  return event.charCode;
 } else {
  return event.keyCode;
 }
}

getClipboardText: function(event){
  var clipboardData = (event.clipboardData || window.clipboardData);
  return clipboardData.getData("text");
 }

setClipboardText: function(event, value){
  if (event.clipboardData){
   return event.clipboardData.setData("text/plain", value);
  } else if (window.clipboardData){
   return window.clipboardData.setData("text", value);
  }
 }