AngularJS Multi select checkboxes

gistfile1.html

<input type="checkbox"
  ng-model="$scope.master"
  ng-checked="$scope.masterChecked"
  ng-click="$scope.masterChange()">

<div ng-repeat="item in items">
  <input type="checkbox"
    ng-model="$scope.isSelected[$index]"
    ng-change="$scope.isSelectedChange($index)"
    ng-checked="$scope.checkedAll">
</div>

gistfile2.js

$scope.masterChange = masterChange;
$scope.isSelectedChange = isSelectedChange;
$scope.checkedAll = false;
$scope.masterChecked = false;

function masterChange() {
  if ($scope.masterChecked) {
    for(var key in $scope.isSelected){
      $scope.isSelected[key] = false;
    }
    $scope.masterChecked = false;
  } else {
    if($scope.master) {
      $scope.checkedAll = true;
    } else {
      $scope.checkedAll = false;
    }
  }
}

function isSelectedChange(index) {
  $scope.masterChecked = true;
}