Creating Above Tree
let root = new Node ( 10 ) ; root . left = new Node ( 20 ) ; root . right = new Node ( 30 ) ; root . left . right = new Node ( 40 ) ; root . left . right = new Node ( 50 ) ; root . right . left = new Node ( 60 ) ; root . right . right = new Node ( 70 ) ; insertChildrenCount ( root ) ; document . write ( " " + randomNode ( root ) + " " ) ;