how to get data from json file using angularjs

I am getting data from json file to display in a table, but first time only i got data from getdata() next time i got following error: Uncaught TypeError: Cannot read property 'length' of undefined Controller.js:95

$http return value is fine, i got all data from json file first time, next time i could not get data from getdata(). getData() function is not working properly, it is working only first time, next time i could not get data.

how to solve this issue.

controller.js

    var app = angular.module('main', ['ngTable', 'claimApp']); 
    app.controller('DemoCtrl', function ($scope, $filter, ngTableParams, appFactory,$http) {
   $scope.datasets = ["1", "2", "3"];
   $scope.dataset = "1"; 
   var data1 = [];
var data2 = []; 
var data3 = []; 
$scope.totalCnt = function () {
    return window.document.getElementById("tablesort").getElementsByTagName("TR").length - 1;
}; 

var getData = function () {  
    if ($scope.dataset == "1") { 
         $http.get('json/json0.json').success(function(data) {
           data1 = data; 
          });  
        return data1; 
    } else if ($scope.dataset == "2") { 
           $http.get('json/json1.json').success(function(data) {
           data2= data;   
          });  
           return data2; 
    } else if ($scope.dataset == "3") { 
               $http.get('json/json2.json').success(function(data) {
           data3= data;   
          });  
          return data3; 
    } 
};
$scope.$watch("dataset", function () { 
    $("#tablesort").fadeOut('slow', function () { 
        $scope.tableParams.reload();
        $scope.tableParams.page(1); 
        $("#tablesort").fadeIn('slow');   
    }); 
});
$scope.tableParams = new ngTableParams({
    page: 1, // show first page
    count: 10, // count per page
    sorting: {
        name: 'asc' // initial sorting
    }
}, {
    total: function () { 
        return getData().length;
        console.info("==="+getData().length);
    }, // length of data
    getData: function ($defer, params) {
        var filteredData = getData(); 
        console.info("filteredData"+filteredData);<!--i could not get this data second time only it is working first time-->
        var orderedData = params.sorting() ?
            $filter('orderBy')(filteredData, params.orderBy()) :
            filteredData; 
        var lastPage = (1 + Math.floor((orderedData.length - 1) / params.count())); 
        $("#lastpage").html(lastPage); 
        $defer.resolve(orderedData.slice((params.page() - 1) * params.count(), params.page() * params.count()));

    },
    $scope: {
        $data: {}
    } 
}); 
 });