js如何判断不能输入双引号？

Question

<script type="text/javascript"> function   HTMLEnCode(str) {  
      
            var    s    =    ""; 
            alert(s); 
            if    (str.length    ==    0)    return    "";  
            alert(str);
            s    =    str.replace(/&/g,    "&amp;");  
            s    =    s.replace(/&lt;/g,        "");  
            s    =    s.replace(/>/g,        "&gt;");  
            s    =    s.replace(/789/g,        "123");  
            s    =    s.replace(/\'/g,      "&#39;");  
            s    =    s.replace(/\"/g,      "&quot;");  
            s    =    s.replace(/\n/g,      " <br>");
            
            document.getElementById('pwdanswer').value=s;
    alert( document.getElementById('pwdanswer').value);
        document.getElementById('answer').value=str;
        alert(document.getElementById('answer').value);
            //alert(s); 
           // return    s;  
      }  </script>在这里如何加上判断不能输入双引号？

Answer 1

<script type="text/javascript">function HTMLEnCode(str) {  
            re = /\"/;
            var s = document.getElementById('pwdanswer').value;
            if(re.test(s)) {alert("不能输入双引号"); return false;}
            s = document.getElementById('answer').value;            if(re.test(s)) {alert("不能输入双引号"); return false;}
            var    s    =    ""; 
            alert(s); 
            if    (str.length    ==    0)    return    "";  
            alert(str);
            s    =    str.replace(/&/g,    "&amp;");  
            s    =    s.replace(/&lt;/g,        "");  
            s    =    s.replace(/>/g,        "&gt;");  
            s    =    s.replace(/789/g,        "123");  
            s    =    s.replace(/\'/g,      "&#39;");  
            s    =    s.replace(/\"/g,      "&quot;");  
            s    =    s.replace(/\n/g,      " <br>");
            
            document.getElementById('pwdanswer').value=s;
               alert( document.getElementById('pwdanswer').value);
               document.getElementById('answer').value=str;
               alert(document.getElementById('answer').value);
            //alert(s); 
           // return    s;  
      }  </script>