Collection function calling each item (Like `setModified()`, `getModified()`).

createCollectionProxyFn.js

//------------------------------------------------------------------------------
// Create a function `collection.fnName`.
// The function applies `_.lodashFn` on `collection` and calls `fnName` on
// each item.
// @param   collection  Any collection lodash can process
// @param   fnName      Name of function generated.
// @param   lodashFn    Name of the lodash collection function to apply.
//                      Defaults to 'each'.
function createCollectionProxyFn(collection, fnName, lodashFn) {
  lodashFn = lodashFn || 'each';
  collection[fnName] = function() {
    var args = arguments;
    return _[lodashFn](collection, function(item) {
      return item[fnName].apply(item, args);
    });
  };
}