全选和反选的方法

  function checkAll() {

              var code_Values = document.getElementsByTagName("input");

              for (i = 0; i < code_Values.length; i++) {

                  if (code_Values[i].type == "checkbox") {

                      code_Values[i].checked = true;

                  }

              }

          }

          function uncheckAll(){

              var code_Values = document.getElementsByTagName("input");

              for (i = 0; i < code_Values.length; i++) {

                  if (code_Values[i].type == "checkbox") {

                      code_Values[i].checked = false;

                  }  

             }

          }

          function check() {

              if (document.getElementById("allcheck").checked == true) {

                  checkAll();

              }

              else {

                  uncheckAll();

              }

          }