not quite

gistfile1.txt

function sortByPath(arr, path) {
  var index, values, returnArr;
  console.log(arguments);
  var argsList = Array.prototype.slice.call(arguments,2);
  var possibleFunc = argsList.splice(-1,1)[0];
  console.log('possibleFunc', possibleFunc);
  console.log('argsList', argsList);
  var compare = function (a,b) {
    if (a < b) {
      return -1;
    } else if (a > b) {
      return 1;
    }
    return 0
  }

  if (typeof possibleFunc === 'function') {
    console.log('compare function!');
    compare = possibleFunc;
  } else if ( possibleFunc === 'str' ) {
    console.log('string sorting!');
    compare = function (a,b) {
      return b.localeCompare(a);
    }
    return arr.sort(compare);
  } else {
    console.log('default compare!');
    argsList.push(possibleFunc);
  }

  values = [];
  for (index in arr) {
    values.push({value: getValue(arr[index], path, argsList), index: index});
  }
  
  values.sort(function (a,b) {
    return compare(a.value, b.value);
  });
  console.log(values);
  returnArr = [];
  for (index in values) {
    originalItem = arr[values[index].index];
    returnArr.push(originalItem);
  }
  
  return returnArr;
}

function getValue(object, path, argsList) {
  var part, partIndex, pathParts, currentItem, match, numArgs;
  var paramList = [];
  pathParts = path.split('.');
  currentItem = object;
  for (partIndex in pathParts) {
    part = pathParts[partIndex];
    if (match = part.match(/([^[]*)\[([\d]*)]/)) {
      console.log('match1!', match);
      // access array element at current object
      currentItem = currentItem[match[1]][match[2]];
    } else if (match = part.match(/([^(]*)\(([\d]*)\)/)) {
      console.log('match2!', match);
      numArgs = match[2];
      while (numArgs--) {
        paramList.push(argsList.shift());
      }
      currentItem = currentItem[match[1]].call(currentItem, paramList);
      // get number of args from argsList using splice
    } else {
      console.log('nomatch!', part);
      currentItem = currentItem[part];
    }
    console.log('--->', currentItem);
  }
  return currentItem;  
}