app.js

angular.module('app')
    .config(configFn)
    .factory('AuthInterceptor', AuthInterceptor);

/* @ngInject */
function configFn($httpProvider) {
    $httpProvider.interceptors.push('AuthInterceptor');
}

/* @ngInject */
function AuthInterceptor($rootScope, $q, secureStore) {
    var interceptor = {
        request: requestFn,
        response: responseFn,
    };

    function requestFn() {
        config.headers = config.headers || {};
        var token = secureStore.get('token');
        if (!!token) { // token exists?
            config.headers.Authorization = 'Bearer ' + token;
        }
        return config;
    }

    function responseFn() {
        if (response.status === 401) {
            console.log('401 Unauthorized');
        }
        return response || $q.when(response);
    }

    return interceptor;
}