gistfile1.js

var directive = {
  'li':{
    'animal<-animals':{
      'span.name':'animal.name'
    },
    
    // at the same level of the <- loop declaration
    // use the keyword: filter

    filter:function(a){
      
      // if the name starts with "a" or "A", keep it, returns true
      // otherwise, skip it, return false
      
      return ( /^a/i ).test( a.item.name );
      
    }
  }
};