[jQuery] data is null,while i need ""

[Junhua Gao]

$.getJSON('/VersionQueryJsonAction',{verID:verid},function(data){
      $('#verMailDate').attr("value",data.verMailDate);
      $('#statementName').attr("value",data.statementName);
})//CampaignJsonAction,function,getJSON


if data.verMailDate is null,i need it is "",not "null",who can help me?