TypeError: Cannot read property 'client_secret' of undefined code example

Example: Cannot destructure property 'client_secret' of 'credentials.installed'

var clientSecret = credentials.installed.client_secret;
In this line credentials is pointing to client_secret.json
so the first key has to be "installed". In my case the key was
"web" and that was causing the error. 
I just renamed the key "web" to "installed".