title: Correct "select all" checkbox with jQuery
body: <p><a href="http://briancray.com/tests/checkboxes/index.html" rel="nofollow noreferrer">http://briancray.com/tests/checkboxes/index.html</a></p>
  
  <p>The ways to implement select all is simple, but not perfect. The select all and unselect all works fine, but when under select all state, if you uncheck one the select all is also checked. How can this be corrected?</p>
  
  <p><img src="https://i.stack.imgur.com/kEVuE.jpg" alt="enter image description here"> </p>
  
  <p>then </p>
  
  <p><img src="https://i.stack.imgur.com/DcvpL.jpg" alt="enter image description here"></p>
  
  <p>"Check all" is still checked. How can this be corrected?</p>