如何在ng-click Angular js上更新数组项？

<div ng-app="myApp" ng-controller="myCtrl">
  <ul>
    <li ng-repeat="item in items">{{ item }}</li>
  </ul>
  <button ng-click="updateItem()">更新数组项</button>
</div>

var app = angular.module('myApp', []);

app.controller('myCtrl', function($scope) {
  $scope.items = ['项1', '项2', '项3'];

  $scope.updateItem = function() {
    // 更新数组项
    $scope.items[1] = '新的项2';
  };
});