How to $watch multiple variables?

Question

I do have two $scope variables. They are called $scope.image and $scope.titleimage.

Basically the store the same type of contents.

Answer 1

$watch method accepts a function as first parameter (beside a string). $watch will "observe" the return value of the function and call the $watch listener if return value is changed.

$scope.$watch(
  function(scope){
    return {image: scope.image, titleImage: scope.titleImage};
  }, 
  function(images, oldImages) {
    if(oldImages.image !== images.image){
      console.log('Image changed');
    }
    if(oldImages.titleImage !== images.titleImage){
      console.log('titleImage changed');
    }
  }, 
  true
); 

Also you might observe a concatenated value, but that doesn't let you know which one of the observed values actually changed:

$scope.$watch('image + titleImage',
  function(newVal, oldVal) {
    console.log('One of the images have changed');
  }
); 

And you can also watch an array of scope variables:

$scope.$watch('[image, titleImage]',
  function(images, oldImages) {
    if(oldImages[0] !== images[0]){
      console.log('Image changed');
    }
    if(oldImages[1] !== oldImages[1]){
      console.log('titleImage changed');
    }
  },
  true
);