gistfile1.js

// Ember.computed.slice managing the array
Ember.computed.slice = function(dependentKey, begin, end) {
  var size = end - begin,
      slicedIndex;
  var options = { 
    addedItem: function(array, item, changeMeta, instanceMeta) {
      slicedIndex = changeMeta.index - begin;
      if (slicedIndex >= 0 && slicedIndex < size) {
        if (slicedIndex >= array.length) {
          array.push(item);
        } else {
          array.insertAt(changeMeta.index - begin, item);                                                                                                                                                                                     
        }   
        if (array.length > size) {
          array.pop();
        }   
      }   
      return array;
    },  
    removedItem: function(array, item, changeMeta, instanceMeta) {
      slicedIndex = changeMeta.index - begin;
      if (slicedIndex >= 0 && slicedIndex < size) {
        array.removeAt(slicedIndex);
        if (changeMeta.arrayChanged.length > size) {
          var fill = changeMeta.arrayChanged[end];
          if (fill) { array.push(fill); }
        }   
      }   
      return array;
    }   
  };  

  return Ember.arrayComputed(dependentKey, options);
};