问AngularJS .length返回TypeError

EN

    angular.module('someApp')
     .filter('filterSomeData',['$filter',function ($filter) {
      return function (items, keyObj) {
    var filterObj = {
      data:items,
      filteredData:[],
      applyFilter : function(query,key){
        var fData = [];
        //unfiltered data at the start
        if(this.filteredData.length === 0){
          this.filteredData = this.data;
        }
        if(query){              
          var fObj = {};         
          if(!angular.isArray(query)){
            fObj[key] = query;
            angular.forEach(fObj, function(fObj, i){
                    fData = fData.concat(
                      $filter('filter')
                      (this.filteredData,fObj));
                }, this);
            console.log(this.filteredData);
          }
          else if(angular.isArray(query)){
            console.log(query);
            if(query.length > 0){ 
              for(var i=0;i<obj.length;i++){
                if(angular.isDefined(query[i])){
                  fObj[key] = query[i];
                  angular.forEach(fObj, function(fObj, i){
                          fData = fData.concat(
                            $filter('filter')
                            (this.filteredData,fObj));
                      }, this);
                }
              }

            }                   
          }                 
          if(fData.length > 0){
            this.filteredData = fData;
          }
          else{
            this.filteredData;
          }
        }
      }
  };

  if(keyObj){
    angular.forEach(keyObj,function(query,key){
      filterObj.applyFilter(query,key);          
    });     
  }

  return filterObj.filteredData;      
}