js/libs/ember-1.5.1.js
function(index, match) {
    var returnValue = -1,
        itemType = match ? RETAIN : FILTER,
        self = this;

    this._findOperation(index, function(operation, operationIndex, rangeStart, rangeEnd, seenInSubArray) {
      var newOperation, splitOperation;

      if (itemType === operation.type) {
        ++operation.count;
      } else if (index === rangeStart) {
        // insert to the left of `operation`
        self._operations.splice(operationIndex, 0, new Operation(itemType, 1));
      } else {
        newOperation = new Operation(itemType, 1);
        splitOperation = new Operation(operation.type, rangeEnd - index + 1);
        operation.count = index - rangeStart;

        self._operations.splice(operationIndex + 1, 0, newOperation, splitOperation);
      }

      if (match) {
        if (operation.type === RETAIN) {
          returnValue = seenInSubArray + (index - rangeStart);
        } else {
          returnValue = seenInSubArray;
        }
      }

      self._composeAt(operationIndex);
    }, function(seenInSubArray) {
      self._operations.push(new Operation(itemType, 1));

      if (match) {
        returnValue = seenInSubArray;
      }

      self._composeAt(self._operations.length-1);
    });

    return returnValue;
  }
function(index, match) {
    var returnValue = -1,
        itemType = match ? RETAIN : FILTER,
        self = this;

    this._findOperation(index, function(operation, operationIndex, rangeStart, rangeEnd, seenInSubArray) {
      var newOperation, splitOperation;

      if (itemType === operation.type) {
        ++operation.count;
      } else if (index === rangeStart) {
        // insert to the left of `operation`
        self._operations.splice(operationIndex, 0, new Operation(itemType, 1));
      } else {
        newOperation = new Operation(itemType, 1);
        splitOperation = new Operation(operation.type, rangeEnd - index + 1);
        operation.count = index - rangeStart;

        self._operations.splice(operationIndex + 1, 0, newOperation, splitOperation);
      }

      if (match) {
        if (operation.type === RETAIN) {
          returnValue = seenInSubArray + (index - rangeStart);
        } else {
          returnValue = seenInSubArray;
        }
      }

      self._composeAt(operationIndex);
    }, function(seenInSubArray) {
      self._operations.push(new Operation(itemType, 1));

      if (match) {
        returnValue = seenInSubArray;
      }

      self._composeAt(self._operations.length-1);
    });

    return returnValue;
  }
Track that an item was added to the tracked array.

@method addItem

@param {number} index The index of the item in the tracked array.
@param {boolean} match `true` iff the item is included in the subarray.

@return {number} The index of the item in the subarray.