What is constant

A constant can be injected everywhere. A constant can not be intercepted by a decorator, that means that the value of a constant should never be changed (though it is still possible to change it programmatically in Angular 1.x).

angular.module('app', []);

app.constant('MOVIE_TITLE', 'The Matrix');

.controller('MyController', function (MOVIE_TITLE) {
  expect(MOVIE_TITLE).toEqual('The Matrix');
});