Javascript 当用户取消提示时，如何防止在空值上填充textarea？

这是我设计的一个工具的一部分，用于在测试hi-cap数据电路时做出统一、清晰的注释，这是一种简单的方法，不必完全修改我的代码，以防止在用户取消提示时将以下内容填充到空值的textarea？写这篇文章时，我完全忘记了布尔值。。。啊！！！！我已经试过了！=“null”是有条件的，这样就不会完全填充textarea

<!-- Remarks Textarea Begin --><td><textarea
 id="REMARKSTEXTAREA" rows="10" cols="100">***CCSC***
      </textarea></td>
<!-- Remarks Textarea End -->

<!-- BEGIN ACCESS DROPDOWN MENU -->
      <td style="text-align: center; width: 638px;">
      <select id="accessdropdownmenu">
      <option value="">MAKE A SELECTION</option>
      <option value="1">ACCESSED CLLI @ XXX IN "A"
DIRECTION…</option>
      <option value="2">ACCESSEDCLLI @ XXX IN "Z"
DIRECTION…</option>
      <option value="3">ACCESSED CLLI @ XXX (FULLY
IMBEDDED) IN "A" DIRECTION…</option>
      <option value="4">ACCESSED CLLI @ XXX (FULLY
IMBEDDED) IN "Z" DIRECTION…</option>
      <option value=" GETTING IMMEDIATE AIS ALARM…">GETTING
IMMEDIATE AIS ALARM…</option>
      <option value=" GETTING IMMEDIATE RAI ALARM…">GETTING
IMMEDIATE RAI ALARM…</option>
      <option value="5">XXX MAPPED CORRECTLY TO XXX PER
CLR/DLR…</option>
      <option
 value=" CROSS CONNECTS DO NOT MATCH PER CLR/DLR INFO...">CROSS
CONNECTS DO NOT MATCH PER CLR/DLR INFO...</option>
      <option value=" NO DACS TEST POINTS PER CLR/DLR…">NO
DACS TEST POINTS PER CLR/DLR…</option>
      <option value=" NO REMOTE TEST ACCESS POINTS PER CLR/DLR…">NO
REMOTE TEST ACCESS POINTS PER CLR/DLR…</option>
      <option value="6">UNABLE TO ACCESS CLLI @ XXX...</option>
      </select>
      <script>
var mytextboxaccess = document.getElementById('REMARKSTEXTAREA');
var mydropdownaccess = document.getElementById('accessdropdownmenu');
mydropdownaccess.onchange = function(){
if (mydropdownaccess.value == 1) {
var CLLI = prompt("WHAT CLLI CODE ARE YOU ACCESSING?");
var ACCESSPOINT = prompt("WHAT ACCESS POINT ARE YOU USING?");
mytextboxaccess.value = mytextboxaccess.value + " ACCESSED " + CLLI + " @ " + ACCESSPOINT + " IN 'A' DIRECTION.."; this.value = "";}
if (mydropdownaccess.value == 2) {
var CLLI = prompt("WHAT CLLI CODE ARE YOU ACCESSING?"); var ACCESSPOINT = prompt("WHAT ACCESS POINT ARE YOU USING?");
mytextboxaccess.value = mytextboxaccess.value + " ACCESSED " + CLLI + " @ " + ACCESSPOINT + " IN 'Z' DIRECTION.."; this.value = "";}
if (mydropdownaccess.value == 3) {
var CLLI = prompt("WHAT CLLI CODE ARE YOU ACCESSING?");
var ACCESSPOINT = prompt("WHAT ACCESS POINT ARE YOU USING?");
mytextboxaccess.value = mytextboxaccess.value + " ACCESSED " + CLLI + " @ " + ACCESSPOINT + " (FULLY IMBEDDED) IN 'A' DIRECTION.."; this.value = "";}
if (mydropdownaccess.value == 4) {
var CLLI = prompt("WHAT CLLI CODE ARE YOU ACCESSING?");
var ACCESSPOINT = prompt("WHAT ACCESS POINT ARE YOU USING?");
mytextboxaccess.value = mytextboxaccess.value + " ACCESSED " + CLLI + " @ " + ACCESSPOINT + " (FULLY IMBEDDED) IN 'Z' DIRECTION.."; this.value = "";}
if (mydropdownaccess.value == 5) {
var ACCESSPOINT1 = prompt("WHAT ACCESS POINT DID YOU ACCESS?");
var ACCESSPOINT2 = prompt("WHAT ACCESS POINT IS IT MAPPED TO?"); mytextboxaccess.value = mytextboxaccess.value + " " + ACCESSPOINT1 + " MAPPED CORRECTLY TO " + ACCESSPOINT2 + " PER CLR/DLR.."; this.value = "";}
if (mydropdownaccess.value == 6) {
var CLLI = prompt("WHAT CLLI CODE WERE YOU ATTEMPTING TO ACCESS?");
var ACCESSPOINT = prompt("WHAT ACCESS POINT WERE YOU USING?");
mytextboxaccess.value = mytextboxaccess.value + " UNABLE TO ACCESS " + CLLI + " @ " + ACCESSPOINT + ".."; this.value = "";}
else {
mytextboxaccess.value = mytextboxaccess.value + mydropdownaccess.value + ".."; this.value = "";}
}
      </script>
      </td>
<!-- END ACCESS DROPDOWN MENU -->

***CCSC***
挑选
在“A”中访问了CLLI@XXX
方向…
在“Z”中访问XXX的CLLI
方向…
访问CLLI@XXX（完全
嵌入）在“A”方向…
访问CLLI@XXX（完全
嵌入）在“Z”方向…
得到
即时AIS警报…
得到
即时RAI警报…
XXX根据正确映射到XXX
CLR/DLR…
交叉
根据CLR/DLR信息连接不匹配。。。
不
每个CLR/DLR的DACS测试点…
不
每个CLR/DLR的远程测试访问点…
无法访问CLLI@XXX。。。
var mytextboxaccess=document.getElementById（'remarkTextArea'）；
var mydropdownaccess=document.getElementById（'accessdropdownmenu'）；
mydropdownaccess.onchange=函数（）{
如果（mydropdownaccess.value==1）{
var CLLI=prompt（“您正在访问什么CLLI代码？”）；
var ACCESSPOINT=prompt（“您使用的是什么接入点？”）；
mytextboxaccess.value=mytextboxaccess.value+“已访问”+CLLI+“@”+ACCESSPOINT+”在“A”方向..”；this.value=“”；}
如果（mydropdownaccess.value==2）{
var-CLLI=prompt（“您正在访问什么CLLI代码？”）；var-ACCESSPOINT=prompt（“您正在使用什么访问点？”）；
mytextboxaccess.value=mytextboxaccess.value+“已访问”+CLLI+“@”+ACCESSPOINT+”在“Z”方向..”；this.value=“”；}
如果（mydropdownaccess.value==3）{
var CLLI=prompt（“您正在访问什么CLLI代码？”）；
var ACCESSPOINT=prompt（“您使用的是什么接入点？”）；
mytextboxaccess.value=mytextboxaccess.value+“已访问”+CLLI+“@”+ACCESSPOINT+“（完全嵌入）在“A”方向..”；this.value=“”；}
如果（mydropdownaccess.value==4）{
var CLLI=prompt（“您正在访问什么CLLI代码？”）；
var ACCESSPOINT=prompt（“您使用的是什么接入点？”）；
mytextboxaccess.value=mytextboxaccess.value+“已访问”+CLLI+“@”+ACCESSPOINT+“（完全嵌入）在“Z”方向..”；this.value=“”；}
如果（mydropdownaccess.value==5）{
var ACCESSPOINT1=prompt（“您访问了什么访问点？”）；
var ACCESSPOINT2=prompt（“它映射到什么访问点？”）；mytextboxaccess.value=mytextboxaccess.value+“”+ACCESSPOINT1+”根据CLR/DLR..正确映射到“+ACCESSPOINT2+”；this.value=“”；}
如果（mydropdownaccess.value==6）{
var CLLI=prompt（“您试图访问什么CLLI代码？”）；
var ACCESSPOINT=prompt（“您使用的是什么接入点？”）；
mytextboxaccess.value=mytextboxaccess.value+“无法访问”+CLLI+“@”+ACCESSPOINT+”。“this.value=”“；}
否则{
mytextboxaccess.value=mytextboxaccess.value+mydropdownaccess.value+”。“this.value=”“；}
}

很遗憾，我无法发表评论，但你说你试过了

if(CLLI != "null") {
   // do stuff
}

应该是：

if (CLLI !== null) {
  // do stuff 
}

解决此问题的另一种方法是使用运算符

一个例子可能是

if (mydropdownaccess.value == 1) {
     var CLLI = prompt("WHAT CLLI CODE ARE YOU ACCESSING?");
     CLLI = (CLLI !== null) ? " ACCESSED " + CLLI : '';
     mytextboxaccess.value = mytextboxaccess.value + CLLI + " @ " + ACCESSPOINT + " (FULLY IMBEDDED) IN 'Z' DIRECTION.."; this.value = "";}
}

然而，花一些时间重构代码可能对您有利