function isConnected(targetNode, otherNode)
   {
      return targetNode.index === otherNode.index || linkedByIndex[targetNode.index + ',' + otherNode.index];
   }
function isConnected(targetNode, otherNode)
   {
      return targetNode.index === otherNode.index || linkedByIndex[targetNode.index + ',' + otherNode.index];
   }
function isConnected ( targetNode , otherNode ) { return targetNode . index === otherNode . index || linkedByIndex [ targetNode . index + ',' + otherNode . index ] ; }
Checks if a target node is connected to another given node by checking `index` or the `linkedByIndex` map.

@param {object}   targetNode
@param {object}   otherNode

@returns {boolean}
Checks if a target node is connected to another given node by checking index or the linkedByIndex map .