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 <= 1'b0; 2'b10 : Q <= 1'b1; 2'b11 : Q <= ~Q; endcase end end endmodule