javascript - $watch a variable for change angularjs -

i'm new complex angular directives. have variable in rootscope called $root.page. have set watch so:

$scope.$watch(   "$root.page",   function handlechange( newvalue, oldvalue ) {     //show select page on page change      console.log(oldvalue, newvalue);      if (!oldvalue || oldvalue !== newvalue) {       $scope.showselectonly = true;     }   } ); 

the way code structured, $scope.showselectonly true. want $scope.showselectonly true when there change $root.page , want false in other cases (i.e. when there no change $root.page variable).

i don't think need watch case. might want using angular value instead. have access angular value in entire angular module app. that, can update showselectonly when page changed.

angular.module('myapp', [])   .value('page', true)   .value('showselectonly', true); 

you can inject page controller in module, , update both values needed.

angular.module('myapp')   .controller('myctrl', function (page, showselectonly) {       if (!page) {          showselectonly = true;       }   });