title: callback.call is not a function
body: <p>I am getting this error and having a difficult time correcting it. I get the following error message: callback.call is not a function</p>
  
  <p>I have posted code snippets below for comment, it seems that the error is being triggered when validateCheckBox(o) is invoked. I understand that the error is triggered from a function being out of context but not exactly sure how to fix.</p>
  
  <pre><code>function checkLength( o, n, min, max ) {
      console.log( arguments.length );
      if ( arguments.length &lt; 4 ) {   
          // issue here with callback.call is not a function
          if ( validateCheckBox(o) ){
              validateCheckBox(o);  
          }
      }else {
          if ( o.val().length &gt; max || o.val().length &lt; min ) {
          o.addClass( "ui-state-error" );
          updateTips( "Length of " + n + " must be between " +
            min + " and " + max + "." );
          return false;
        } else {
          return true;
        }
  
      }
  
  }
  
  function validateCheckBox( o ) {
  
      var css = $(".border").css({
                                  "border-color": "",
                                  "border-weight": "",
                                  "border-style" : "",
                                  "background-color": "",
                                  "background-image": "",
                                  "background-repeat":"",
                                  "background-position":""
                              });
      //console.log(css);
      var invalidChkBox = {   
                          "border-color":"#cd0a0a",
                          "border-weight":"1px",
                          "border-style":"solid",
                          "background-color": "#feflec",
                          "background-image": "url('lib/jquery-ui/css/images/ui-bg_glass_95_fef1ec_1x400.png')",
                          "background-repeat": "repeat-x",
                          "background-position": "50% 50%"
  
  
              }
  
      // throwing error callback is not defined
      var isChecked = $( "#verification" ).is(":checked");
  
      if ( isChecked == false || isChecked == undefined ) {
  
          $( ".border"  ).css( invalidChkBox );
          o.addClass( "ui-state-error" );
          $( ".validateTips" ).text( "You must agree that all information is accurate and true, by checking the box." );
  
      }else{
          // reported bug callback.call is not a function @error below
          $( ".validateTips" ).css( 'display', null ).text( "" );
          $( ".border"  ).css( css );
  
  
  
      }
  
  
  }
  
   valid = valid &amp;&amp; checkLength ( verification, "Verification", 1 );
  </code></pre>
  
  <p>Thanks in advance.</p>