How to Disable html form with javascipt?
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in this script, I have two Selection button, n want to make the validation for it. The user must select one of them, n I hope if the user choose one of them, the other Selection will be disabled automatically,

this my script

 

    <html>
       <head>
          <script type="text/javascript">
            function Check()  //this the funciton for diasbled
    	{
    	  var x =document.getElementById("supexp1");
    	  var y =document.getElementById("supexp2");
    	  
    	  if(x.value != "")
    	  {
    	    document.form1.supexp2.disabled=true;
    	  }
          else if(y.value != "")
          {
            {
    	    document.form1.supexp1.disabled=true;
    	  }
          } 
        }
          
          </script>
          
       </head>
      <body>
        <form method="POST" action="destination.php" id="form1">
           <select name="SUPEXP" id="supexp1" data-native-menu="false" onChange="Check()">
               <option >Ekspedisi Local1</option>  //this selection 1 
               <option >Ekspedisi Local2</option>  //this selection 1 
               <option >Ekspedisi Local3</option>  //this selection 1
          
           </select>
        <select name="SUPEXP" id="supexp2" data-native-menu="false" onChange="Check2()">
               <option >Ekspedisi Expor2</option>  //this selection 2
               <option >Ekspedisi Expor2</option>  //this selection 2
               <option >Ekspedisi Expor2</option>  //this selection 2
        
           
        </select>
        </form>
      </body>
     </html>


I use the jquerymobile framework and selection connect to the database. That code(javascript) not run.
Can Anyone help me for fix the validation? I really appreciate your answer