如何通过ajax无刷新评论功能？

//去掉左右尖括号 并用去掉空格后的字符串替代显示 
function replaceBrackets(id) { 
 var inputValue = $("#" + id).val(); 
 while (inputValue.indexOf("<") != -1) { 
  inputValue = inputValue.replace("<", "["); 
 } 
 while (inputValue.indexOf(">") != -1) { 
  inputValue = inputValue.replace(">", "]"); 
 } 
 while (inputValue.indexOf("&") != -1) { 
  inputValue = inputValue.replace("&", " "); 
 } 
 $("#" + id).val(inputValue); 
} 
 
function replaceChar(name, char) { 
 var inputValue = $("#" + name).val(); 
 while (inputValue.indexOf(char) != -1) { 
  inputValue = inputValue.replace(char, ""); 
 } 
 return inputValue; 
} 
 
$("#txtMessage").blur(function () { 
 $("#txtMessage").val(replaceChar("txtMessage", "<!--")); 
 if ($("#txtMessage").val() == "") { 
  document.getElementById("txtMessage").style.color = "#8C8C8C"; 
  $("#txtMessage").val("没有填写留言内容"); 
  return false; 
 } 
 replaceBrackets("txtMessage"); 
 return true; 
}); 
 
$("#txtMessage").focus(function () { 
 if ($("#txtMessage").val() == "没有填写留言内容") { 
  document.getElementById("txtMessage").style.color = "#000000"; 
  $("#txtMessage").val(""); 
 } 
}); 
 
function txtanum(id, name) //统计txta的输入字数 
{ 
 var maxl = 151; 
 var num = 150; 
 var content = $("#" + id).val(); 
 content.slice(0, maxl); 
 var nowlength = content.length; 
 if (nowlength >= 0) { 
  if (nowlength < num) 
   $("#" + name).text(nowlength); 
  else 
   $("#" + name).text(num); 
 } else 
  $("#" + id).val(content.substring(0, maxl - 1)); 
 
 if (nowlength == 0) 
  $("#" + name).text(0); 
 
 if (nowlength > num) 
  $("#" + id).val(content.substring(0, num)); 
} 
 
 
var isSubmit = false; 
$('#subMessage').click(function () { 
 
 if (isSubmit) { 
  return; 
 } 
 isSubmit = true; 
 if ($("#txtMessage").val() == "没有填写留言内容" || $.trim($("#txtMessage").val()) == "") { 
  alert("请输入留言内容！"); 
  isSubmit = false; 
  return; 
 } 
 $.ajax({ 
  type: "POST", 
  url: app_param.path_context+"/user/member/msgboard/save", 
  data: { "context": ($("#txtMessage").val()) }, 
  error: function () { 
   isSubmit = false; 
  }, 
  success: function (data) { 
   if (data) { 
    addRow(data); 
    isSubmit=false; 
    $('#zanwu').hide(); 
    document.getElementById("txtMessage").style.color = "#8C8C8C"; 
  $("#txtMessage").val("没有填写留言内容"); 
   } 
  } 
 }); 
 function addRow(messageboard) { 
  var table = $("#tblmsg"); 
  var html = []; 
  html.push("<tr>"); 
  html.push("<td class='m_time'>"); 
  html.push(messageboard.createDate); 
  html.push("</td>"); 
  html.push("<td>"); 
  html.push(messageboard.context); 
  html.push("</td>"); 
  html.push("<td style='border-right: 0;' class='m_order_procz'>"); 
  html.push("<a class='xxx' href='messagereply/"+messageboard.id+"'>查看</a>"); 
  html.push("</td>"); 
  html.push("</tr>"); 
  html = html.join(''); 
  table.append(html); 
 } 
 
});