How to validate radio button in html using Javascript?
<p>how can i validate the input of radio button?
Currently,i doing a survey form using radio button. I have try many way to validate the radio but all the code are unusable. Anyone can help?TQ. 
Below is my code</p>

<p><div class="snippet" data-lang="js" data-hide="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>var f = document.frmSubmit;    

        var radios = document.getElementsByName('appbk')

     for (var i = 0; i &lt; radios.length; i++) {
         if (document.getElementById("appbk") == false) {
         alert('Remarks has exceeded allowable radio characters.');
         f.appbk.focus();
         return false; // checked
     }
     }

        if (f.FEEDBACK_MSG.value != "" ) { 
         if (f.FEEDBACK_MSG.value.length &gt; 500 ){   
    bootbox.alert('Remarks has exceeded allowable maximum characters.');
    f.FEEDBACK_MSG.focus();
    return false;
   } 
  }

        return true;
        document.getElementById("btnsubmit").disabled = true;
    }</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;tr&gt;
  &lt;td&gt;&lt;div class="text2"&gt;Appointment Booking &lt;/div&gt;&lt;/td&gt;
  &lt;td&gt;&lt;div class="text3"&gt;
   &lt;span style="margin:0 30px;"&gt;&lt;input type="radio" id="appbk1" name="appbk" value="1"&gt;&lt;lable&gt;1&lt;/lable&gt;&lt;/span&gt;
   &lt;span style="margin:0 30px;"&gt;&lt;input type="radio" id="appbk2" name="appbk" value="2"&gt;&lt;lable&gt;2&lt;/lable&gt;&lt;/span&gt;
   &lt;span style="margin:0 30px;"&gt;&lt;input type="radio" id="appbk3" name="appbk" value="3"&gt;&lt;lable&gt;3&lt;/lable&gt;&lt;/span&gt;
   &lt;span style="margin:0 30px;"&gt;&lt;input type="radio" id="appbk4" name="appbk" value="4"&gt;&lt;lable&gt;4&lt;/lable&gt;&lt;/span&gt;
   &lt;span style="margin:0 30px;"&gt;&lt;input type="radio" id="appbk5" name="appbk" value="5"&gt;&lt;lable&gt;5&lt;/lable&gt;&lt;/span&gt;
  &lt;/div&gt;
  &lt;/td&gt;
 &lt;/tr&gt;</code></pre>
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