Ajax在项目中简单应用实例：

	var request = false; 
	
	var flag = true;  
  
	//创建XMLHttpRequst对象的一个实例   
	function createRequest()   
	{   
	    if(window.XMLHttpRequest)   
	    {   
	        request = new XMLHttpRequest();   
	    }   
	    else if(window.ActiveXObject)   
	    {   
	        request = new ActiveXObject("Msxml2.XMLHTTP");   
	    }   
	    if (!request){
	    	 alert("Error initializing XMLHttpRequest!");
	    }   
	}  
	
	function getIsNotRepeat() {
	  createRequest(); 
	  var exportDate = document.frmExportSubjectBalance.strExportSubjectBalanceDate.value;
	 
	  var url = "<%=strContext%>/FindExistSubjectBalance.jsp?exportDate=" + exportDate;
	  request.open("GET", url, false);    
	  request.onreadystatechange = updatePage;   
	  request.send(null);   
	}   
	  
	function updatePage() {   
	     if (request.readyState == 4) {   
	       if (request.status == 200) {   
	           var respText = request.responseText;  
	           /* 返回1,科目余额已存在 */
	           if( respText == 1 ){
	           		if(confirm('科目余额已存在，是否重新导入？')){
	           			flag = true;
	           		}else{
						flag = false;       			
	           		}
	           }else{
	           		flag = true;
	           }
	       }   
	    }   
	} 

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