How do you plan to solve it?
module jk_ff_enable ( input CLK, input EN, input J, input K, output reg Q ); always@(posedge CLK) begin if(EN)begin case({J,K}) 2'b00 : Q <= Q; 2'b01 : Q <= 0; 2'b10 : Q <= 1; 2'b11 : Q <= ~Q; endcase end end endmodule