How to eliminate the default option value influence on JS judgement-CodePudding

I set up a number in the JSP drop-down list box, each option has a Value, the default is zero, I hope that the Value of the two channels can't completely the same, the same will pop up an alert box, for example, application of CH1 and CH2 can be "RGDM1 101700" and "RGDM1 102450", but not for "RGDM1 102450" at the same time, it can be judged, but I hope to eliminate the influence of the default Value of 0, the code is as follows:

 & lt; % @ page language="Java" contentType="text/HTML. Charset=utf-8 "% & gt; 
<% @ page import="Java. IO. *" % & gt; 
 
 
 
<meta charset="utf-8" & gt; 
<meta name="viewport" content="width=device - width, initial - scale=1" & gt; 

 UE2020 Web Server Interface 
<meta name="keywords" content="UP2020 Industrial equipment control"/& gt; 
<meta name="description" content="UP2020 Industrial equipment control"/& gt; 

<link rel="stylesheet" type="text/CSS" href="https://bbs.csdn.net/topics/vendor/bootstrap/css/bootstrap.min.css" & gt; 
<link rel="stylesheet" type="text/CSS" href="https://bbs.csdn.net/topics/fonts/font-awesome-4.7.0/css/font-awesome.min.css" & gt; 
<link rel="stylesheet" type="text/CSS" href="https://bbs.csdn.net/topics/fonts/iconic/css/material-design-iconic-font.min.css" & gt; 
<link rel="stylesheet" type="text/CSS" href="https://bbs.csdn.net/topics/css/util.css" & gt; 
<link rel="stylesheet" type="text/CSS" href="https://bbs.csdn.net/topics/css/Intf.css" & gt; 
 
<body> 
PSBC2020 
 

 
 
 
  
 LED 
 IOA 
 Description 
 
 
 CH1 & lt;/th> 
   
   
  
 
 
 CH2 & lt;/th> 
   
   
  
 
 
 CH3 & lt;/th> 
   
   
  
 
 
 CH4 & lt;/th> 
   
   
  
 
 
Onmouseover="this. Style. BackgroundColor='# 6 f6f6f';" onm ouseout="this. Style. BackgroundColor=' ';"/> 

          
          
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