"Controllers polluting the Global Namespace" what does it mean in Angular

Question

I am newbie to Angular.js , i have read that Controllers should not pollute the global namespace.

What does it really means

and why angular.module('SomeApp',[]).controller('SomeController', function($scope) {})

is the best way to add a controller?

Answer 1

Edit: Polluting the global namespace is not specific to Angular, but to Javascript (and actually any dynamic-typed language, where variables could appear or be redeclared in almost any scope).

Polluting the global namespace would make unavailable -actually: will override- certain names among modules.

Imagine I have a module A in 'a.js' where I declare:

mymodule = angular.module('A');

function Foo($s, $http){ ... };
foo = mymodule.controller('foo', ['$scope', Foo]);

Also imagine I included, beforehand, a script named 'utils.js':

foo = 3;

foo in a.js would override foo in my utils script. That is polluting the global namespace and that's why it's a bad idea (perhaps I actually NEEDED the foo var).

Want to have code like that instead of chaining the calls? use a closure:

/* a.js */
(function(){
    var mymodule = angular.module('A');

    function Foo($s, $http){ ... };
    var foo = mymodule.controller('foo', ['$scope', Foo]);
})();

And so, you will not pollute the global namespace since each declaration is inside the anonymous function call.