$scope.arrTitle is already a new variable (array)

When you modify $scope.arrTitle[0], you only modify the data of its first element.

$scope.arrTitle = [$scope.title1, $scope.title2]; Just assign an initial value to the array.

When you want to change $scope.arrTitle[0], $scope.title1 will also change, then use $scope.$watch

In fact, you can declare arrTitle as an object

$scope.arrTitle = { title1: "标题1", title2: "标题2" }; //修改 $scope.arrTitle.title1 = "xx";