在Python中，视图和浅拷贝之间有什么区别？(In Python, what's the difference between a view and a shallow copy?)

 你只需要UNBIND一个处理程序 
 
 $(document).ready(function() {
  $('#states').change(function() {

    $( "#stateinfo").unbind( "keypress" );

    var dropdown = $("#states").val();
    if (dropdown == "State") {
      $("#stateinfo").val("");
      $("#stateinfo").attr('disabled', 'disabled');
    } else if (dropdown == "TX") {
        $('#stateinfo').keypress(function(e) {
        var regex = new RegExp("^[0-9]+$");
        var num = String.fromCharCode(!e.charCode ? e.which : e.charCode);
        if (regex.test(num)) {
          return true;
        }
        e.preventDefault();
        return false;
      });
      $("#stateinfo").removeAttr('disabled');
      $("#stateinfo").val("");
      $("#stateinfo").attr("maxlength", "10");
    } else {
      $('#stateinfo').keypress(function(e) {
        var regex = new RegExp("^[a-zA-Z0-9]+$");
        var str = String.fromCharCode(!e.charCode ? e.which : e.charCode);
        if (regex.test(str)) {
          return true;
        }
        e.preventDefault();
        return false;
      });
      $("#stateinfo").removeAttr('disabled');
      $("#stateinfo").val("");
      $("#stateinfo").attr("maxlength", "15");
    }
  });
});

You just need UNBIND a handler 
 
 $(document).ready(function() {
  $('#states').change(function() {

    $( "#stateinfo").unbind( "keypress" );

    var dropdown = $("#states").val();
    if (dropdown == "State") {
      $("#stateinfo").val("");
      $("#stateinfo").attr('disabled', 'disabled');
    } else if (dropdown == "TX") {
        $('#stateinfo').keypress(function(e) {
        var regex = new RegExp("^[0-9]+$");
        var num = String.fromCharCode(!e.charCode ? e.which : e.charCode);
        if (regex.test(num)) {
          return true;
        }
        e.preventDefault();
        return false;
      });
      $("#stateinfo").removeAttr('disabled');
      $("#stateinfo").val("");
      $("#stateinfo").attr("maxlength", "10");
    } else {
      $('#stateinfo').keypress(function(e) {
        var regex = new RegExp("^[a-zA-Z0-9]+$");
        var str = String.fromCharCode(!e.charCode ? e.which : e.charCode);
        if (regex.test(str)) {
          return true;
        }
        e.preventDefault();
        return false;
      });
      $("#stateinfo").removeAttr('disabled');
      $("#stateinfo").val("");
      $("#stateinfo").attr("maxlength", "15");
    }
  });
});