Why Angular Js Parameter of a Watch Function Should Be a Scope Variable?

Question

Why Angular Js Parameter of a Watch Function Should Be a Scope Variable?

$scope.myFunc = function(privilege){ 

    $scope.check = function(privilege){
       return ...
    };  

    $scope.$watch('check(privilege)',function(val){
        ...
    }    
}

My privilege variable becomes undefined at every watch check(which must not be)? Why I should define it scope variable or do I miss anything with Angular Js?

angularjs

Answer 1

The first parameter of the $watch method (the "watchExpression") can be either an Angular string expression (that is evaluated against the $scope), or a function, which is called with $scope as the first parameter. There is no way to pass privilege as the first argument to a watchExpression that is a function.

You could create a closure, if you don't want to store the privilege value on the $scope. See Vojta's fiddle for an example. See also https://groups.google.com/forum/#!msg/angular/UJRxn_Y0Dd4/9ha38PC3PCwJ