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) case({J,K}) 2'b00:Q<=Q; 2'b01:Q<=1'b0; 2'b10:Q<=1'b1; 2'b11:Q<=~Q; endcase else Q<=Q; end endmodule