This example will open a configuration portal when no WiFi configuration has been previously entered or when a button is pushed. It is the easiest scenario for configuration but requires a pin and a button on the ESP8266 device. The Flash button is convenient for this on NodeMCU devices. Also in this example a password is required to connect to the configuration portal network. This is inconvenient but means that only those who know the password or those already connected to the target WiFi network can access the configuration portal and the WiFi network credentials will be sent from the browser over an encrypted connection and can not be read by observers.
Repository from Github https://github.comJohnDevine/ESPAsync_WiFiManagerConfigOnSwitch