count number of unique alphabets in each string
for ( let k = 0 ; k < na [ j ] . length ; k ++ ) { let x = na [ j ] [ k ] . charCodeAt ( 0 ) - 65 ; if ( ( na [ j ] [ k ] != ' ' ) && ( character [ x ] == 0 ) ) { c [ j ] ++ ; character [ x ] = 1 ; } }