function bonsaRegnumCheck() {
  dataString = $("#inputform").serialize();
   $.ajax({
             type: "post",
             url: "<%=request.getContextPath()%>/info/certRegnumCheck.do",
             dataType: "text",
             data: dataString,
             success: function(data) { 
              // 사업자번호가 중복되는지 확인
               
              if(document.inputform.regnum.value != ""){
              
               if(data != "0"){
               alert("기존에등록된 사업자번호입니다 확인하세요");
               return;
               }else{
                getCertInstallData();
               }
              }else{
               alert("사업자번호를 입력하세요");
               document.inputform.regnum.focus();
               returm;
              }
             },
             error: function(data) { alert('에러 발생'); }
         });
   
    
}

출처: http://uip80.tistory.com/entry/jquery-jajax-text-타입-호출?category=199706 [여명의집]