Find the number of integers from 1 to n which contains digits 0 ' s ▁ and ▁ 1' s only | Function to find the number of integers from 1 to n which contains 0 ' s ▁ and ▁ 1' s only ; If number is greater than n ; Otherwise add count this number and call two functions ; Driver code
function countNumbers ( x , n ) { if ( x > n ) return 0 ; return 1 + countNumbers ( x * 10 , n ) + countNumbers ( x * 10 + 1 , n ) ; } let n = 120 ; document . write ( countNumbers ( 1 , n ) ) ;