title: Why top input function not work?
body: <p>In Area 1, when I checked checkbox bbbbbb or checkbox cccccc
  input will disable , it's not work</p>
  
  <p>But in Area 2 it's OK</p>
  
  <p>Why Area1 function not work ?</p>
  
  <p>thank you.</p>
  
  <pre><code>Area 1
  &lt;br&gt;
  &lt;input type="text" id="a" name="a"&gt;   
  &lt;br&gt;
  &lt;input type="checkbox" id="b" name="b"/&gt; bbbbbb
  &lt;br&gt;
  &lt;input type="checkbox" id="c" name="c"/&gt; cccccc
  &lt;/div&gt;
  
  &lt;script type="text/javascript"&gt;
  window.onload=function(){
  document.getElementById('b').onchange = function () {
      document.getElementById('c').checked = false;
      document.getElementById('a').disabled = this.checked;
  };
  document.getElementById('c').onchange = function () {
      document.getElementById('b').checked = false;
      document.getElementById('a').disabled = this.checked;
  
  };
  }
  &lt;/script&gt;
  
  &lt;br&gt;
  &lt;br&gt;
  &lt;br&gt;
  &lt;br&gt;
  &lt;br&gt;
  Area 2
  &lt;br&gt;
  
  &lt;input type="text" id="1" name="1"&gt;   
  &lt;br&gt;
  &lt;input type="checkbox" id="2" name="2"/&gt; 222222
  &lt;br&gt;
  &lt;input type="checkbox" id="3" name="3"/&gt; 333333
  &lt;/div&gt;
  
  
  &lt;script type="text/javascript"&gt;
  window.onload=function(){
  document.getElementById('2').onchange = function () {
      document.getElementById('3').checked = false;
      document.getElementById('1').disabled = this.checked;
  };
  document.getElementById('3').onchange = function () {
      document.getElementById('2').checked = false;
      document.getElementById('1').disabled = this.checked;
  
  };
  }
  &lt;/script&gt;
  </code></pre>