Am using the client.js by including it in html with the API_KEY.
And calling as below
var authenticationSuccess = function() {
console.log('Successful authentication' + Trello.token());
};
var authenticationFailure = function() {
console.log('Failed authentication');
};
window.Trello.authorize({
type: 'popup',
name: 'Getting Started Application',
scope: {
read: 'true',
write: 'true' },
expiration: 'never',
success: authenticationSuccess,
error: authenticationFailure
});
Then i see a page with invalid return_url.