how to copy and paste on keydown event in javascript.

function keyPressFunctionForValidations(e) {
              debugger;
              var charCode = (e.which) ? e.which : e.keyCode
              switch (e.type) {
                  case 'keydown':
                      if (e.ctrlKey == true && (charCode == 118 || charCode == 86)) {
                          e.preventDefault();
                          return;
                      }

                      var isValid = (charCode >= 37 && charCode <= 40) || (charCode >= 65 && charCode <= 90) || charCode == 32 || charCode == 46 || charCode == 8 || charCode == 9 || charCode == 67 || charCode == 86 || charCode == 17;
                      if (isValid == false) {
                          e.preventDefault();
                          return;
                      }
                      break;
                  case 'paste':
                      e.preventDefault();
                      return;
                      break;
              }

          }

i have the paste function as follow
 function validateOnPaste(e) {
                debugger;
                var theEvent = e || window.event;
                var key = theEvent.keyCode || theEvent.which;
                key = String.fromCharCode(key);
                var regex = /[a-zA-z]|\s/;
                if (!regex.test(key)) {
                    e.preventDefault();
                    return;
                }
            }