Error while working with okta-auth-js liabrary

Uncaught TypeError: ‘caller’, ‘callee’, and ‘arguments’ properties may not be accessed on strict mode functions or the arguments objects for calls to them.

I am getting that error while using following code:
var idToken = authClient.tokenManager.get(‘idToken’)
.then(idToken => {
// If ID Token exists, output it to the console
if (idToken) {