text: In this loop we count the frequency of element through map m .
code: for ( let i = 0 ; i < n ; ++ i ) { m [ a [ i ] ] ++ ; if ( m . has ( a [ i ] ) ) { m . set ( a [ i ] , m . get ( a [ i ] ) + 1 ) } else { m . set ( a [ i ] , 1 ) } }