Issuing new JWT token only once per user for anonymous authentication - angularjs

Question

I would like to use JWT tokens for anonymous authentication in Angular. I only want to issue a new token to a user if there isn't already one in local storage. When I use the code below, a new token is issued every time the page is refreshed.
Any suggestions on how to prevent this?
Javascript (client side):
myApp.constant('API_URL', 'http://localhost:8080');
myApp.factory('UserFactory', function Userfactory($http, API_URL, AuthTokenFactory, $q) {
return $http.get(API_URL + '/api/authenticate').then(function success(response) {
AuthTokenFactory.setToken(response.data.token);console.log(response.data);
return response;
});
});
myApp.factory('AuthTokenFactory', function AuthTokenFactory($window) {
var store = $window.localStorage;
var key = 'auth-token';
return {
getToken: getToken,
setToken: setToken
};
function getToken() {
return store.getItem(key);
}
function setToken(token) {
if (token) {
store.setItem(key, token);
} else {
store.removeItem(key);
}
}
});
myApp.factory('AuthInterceptor', function AuthInterceptor(AuthTokenFactory) {
return {
request: addToken
};
function addToken(config) {
var token = AuthTokenFactory.getToken();
if (token) {
config.headers = config.headers || {};
config.headers.Authorization = 'Bearer ' + token;
}
return config;
}
});