code: function isInView ( $elem, container, opts ) {
  
          var config,
              elem = $elem[0];
  
          if ( ! $elem.length ) return false;
  
          config = _prepareConfig( $elem, container, opts );
          checkHierarchy( elem, config.container );
  
          return _isInView( elem, config );
  
      }
docs: Does the actual work of $.fn.isInView. Protected from external modification. See $.fn.isInView for details.
  
  @param {jQuery}                                    $elem
  @param {Window|Document|HTMLElement|jQuery|string} [container=window]
  @param {Object}                                    [opts]
  @param {boolean}                                   [opts.partially=false]
  @param {boolean}                                   [opts.excludeHidden=false]
  @param {string}                                    [opts.direction="both"]
  @param {string}                                    [opts.box="border-box"]     alternatively, "content-box"
  @param {number|string}                             [opts.tolerance=0]          number only (px), or with unit ("px" or "%" only)
  
  @returns {boolean}