Auth0.JS - login() in React SPA results in stacktrace

Auth0 noob here. I have had no luck in resolving the following error when calling login():

client.js:752 Uncaught TypeError: Converting circular structure to JSON
at stringify ()
at Request._end (client.js:752)
at Request.end (client.js:676)
at RequestObj.end (request-builder.js:58)
at CrossOriginAuthentication.login (cross-origin-authentication.js:72)
at WebAuth.login (index.js:659)
at Auth.login (Auth.js:30)
at onSubmit (Login.js:88)

Node version is 8.11.2
Auth0.js version is 9.6.0

Any ideas?

Did you follow our quick starts? We have one for react: Auth0 React SDK Quickstarts: Login

Can you post a snippet of how are you calling this method?

Thanks. I resolved the issue. It was that my parameter values were JSON instead of plain text.