Greasemonkey的脚本给出了关于输入错误

Question

我有一个Greasemonkey的脚本逻辑这样的错误：

1. 除非登录的用户是在特权组（JOHN，卢克杰夫，MAX，安迪），使用name="prio"禁用<input>。

2. 如果不是特权用户，则阻止从<input name="dest">中选择值。
   具体而言，请阻止“12”或“22”并写入错误消息。

该脚本工作正常，但有一个错误：

当我在其他输入字段中插入文本或更改一个选择栏，然后按输入，提交停止，我收到在控制台中的错误信息：

Error: destInput[0] has no properties Source File: file:///E:/FirefoxPortable2.x/Data/profile/extensions/%7Be4a8a97b-f2ed-450b-b12d-ee082ba24781%7D/components/greasemonkey.js Line: 379

var err = this.findError(script, line - lineFinder.lineNumber - 1);

我觉得跟name="dest"规则正在对所有输入字段和选择字段？但我只需要“dest”输入的规则。

这里是my script code：

// ==UserScript== 
// @name   _SO Block submit on custom FF2 page. 
// @namespace  PC 
// @include  file:///D:/temp/foo%20SO/task* 
// @include  file:///D:/temp/foo%20SO/fixture* 
// @include  file:///D:/temp/foo%20SO/pallet* 
// ==/UserScript== 

GM_log ("Script start."); 

unsafeWindow._oldSubmit = unsafeWindow.document.forms[0].submit; 
unsafeWindow.document.forms[0].submit = function() { 
    GM_log ("Submit function fired."); 

    var destInput = document.getElementsByName ("dest"); 
    if (! destInput || destInput.length == 0) { 
     //unsafeWindow._oldSubmit(); 
    } 

    var destValue = destInput[0].value; 
    if ( /^\s*$/.test (destValue) 
      || excludedDestinations.indexOf (destValue) > -1 
    ) { 
     GM_log ("Submit should be blocked! (1)"); 
    } 
    else { 
     //unsafeWindow._oldSubmit(); 
    } 
}; 


//--- Make sure this list of names is all uppercase. 
var usersWhoCanSetPriority = ['JOHN', 'LUKE', 'JEFF', 'MAX', 'ANDY']; 
var excludedDestinations = ['12', '22']; 

var bDisablePrio = true; 
var tdNodes   = document.getElementsByTagName ("TD"); 
for (var J = tdNodes.length - 1; J >= 0; --J) { 
    var tdNode  = tdNodes[J]; 
    if (tdNode.className == "user") { 
     var userName  = tdNode.textContent.replace (
      /^(?:.|\n|\r)+\(User:\s+([^)]+)\)(?:.|\n|\r)+$/i, "$1" 
     ).toUpperCase(); 
     if (usersWhoCanSetPriority.indexOf (userName) > -1) { 
      bDisablePrio = false; 
     } 
    } 
} 

if (bDisablePrio) { 
    var oldInput = document.getElementsByName ("prio"); 
    if (oldInput && oldInput.length) { 
     oldInput[0].setAttribute ("disabled", "disabled"); 
    } 

    var destInput = document.getElementsByName ("dest"); 
    if (destInput && destInput.length) { 
     destInput[0].addEventListener (
      "change", 
      function (zEvent) { 
       bCheckdestinationValue (destInput[0]); 
       GM_log ("Change handler fired."); 
      }, 
      false 
     ); 

     destInput[0].form.addEventListener (
      "submit", 
      function (zEvent) { 
       GM_log ("Submit handler fired."); 
       var destValue = destInput[0].value; 
       if ( /^\s*$/.test (destValue) 
         || excludedDestinations.indexOf (destValue) > -1 
       ) { 
        //--- Stop the submit 
        zEvent.preventDefault(); 
        //zEvent.stopPropagation(); 
        GM_log ("Submit should be blocked! (2)"); 
        return false; 
       } 
      }, 
      true 
     ); 
    } 
} 

function bCheckdestinationValue (destInputNd) { 
    //--- Returns true if value is bad. 
    if (excludedDestinations.indexOf (destInputNd.value) > -1) { 
     destInputNd.value = ''; // Blank input 

     //--- Add or show Error message. 
     var destErrNode = document.getElementById ("gmDestErrorDisp"); 
     if (destErrNode) { 
      destErrNode.style.display = "inline"; 
     } 
     else { 
      destErrNode    = document.createElement ('b'); 
      destErrNode.id   = "gmDestErrorDisp"; 
      destErrNode.style.color = "red"; 
      destErrNode.textContent = "12 and 22 are forbidden"; 
      destInputNd.parentNode.appendChild (destErrNode); 
     } 
     return true; 
    } 
    else { 
     var destErrNode = document.getElementById ("gmDestErrorDisp"); 
     if (destErrNode) { 
      destErrNode.style.display = "none"; 
     } 
    } 
    return false; 
} 

Here is an old working version on jsFiddle for a better understanding。

PS：pastebin代码（unsafeWindow ..）是我旧系统上唯一的工作版本。系统运行FF 2.0.0.11和Greasemonkey 0.8，并且无法更新。

有没有一种方法可以消除这个bug？ ：d

Answer 1

变化形式[0] .submit代码：

if (unsafeWindow.document.forms[0]) { 
    unsafeWindow._oldSubmit = unsafeWindow.document.forms[0].submit; 
    unsafeWindow.document.forms[0].submit = function() { 
     GM_log ("Submit function fired."); 

     var destInput = document.getElementsByName ("dest"); 
     if (! destInput || destInput.length == 0) { 
      unsafeWindow._oldSubmit(); 
     } 
     else { 
      var destValue = destInput[0].value; 
      if ( /^\s*$/.test (destValue) 
        || excludedDestinations.indexOf (destValue) > -1 
      ) { 
       GM_log ("Submit should be blocked! (1)"); 
      } 
      else { 
       unsafeWindow._oldSubmit(); 
      } 
     } 
    }; 
} 

它使用它们之前确实做的一个合适的工作存在一定的事情。

另外，去掉这一行：

//zEvent.stopPropagation();