AngularJs(Part 1）

I am tired to translate these into Chinese.

but who cares? i write these posts just for myself

Scope

a new scope is created by the ng-controller directive using
the Scope.$new() method call.
yes , we need to have at least one instance of a scope before
creating a new scope!
so here is the $rootScope. it is the paremt of all the other
scopes. the $rootScope instance gets created when a new
application is bootstrapped.
each scope contains a property $parent which points to its parent scope.

ng-controller is a scope-created directive.
there are many other scope-created directives.

Scopes form a parent-child ,tree-like relationship rooted at
the $rootScope instance. and scopes' creation is driven by the DOM tree.

check the famous ng-repeat.
let's say a HTML snippet<li ng-repeat='per in persons'>{{per.name}}</li>
when interating persons, a new variable needs to be created to hold each per.
it seems the Google does not use the strategy that just simplely override previous value.
instead , it creats a new scope for each per and expose the scope to maybe the parent scope $scope.
in this way, it's possible to create variable with the same name on different scopes without createing name collisions.
in above snippet, every <li> element gets its own scope when the per variable can be defined.

as i say above ,each $scope except the $rootScope contains a property $parent which pointing to parent scope,
so all properties defined in parent scope is actually available to child scope.

Scope's inheritance in AngularJs follws the same rules as prototypical inheritance in JavaScript.(when we try to read
as property, the inheritance tree will be traversed upwards till a property is found.)

Scopes are responsible to creat variables.
they are to provide isolated namespaces and avoid name collisions.
they can be destroyed and the garbage collection will deallocate the resource.