Async.js

sortBy.js

  1. import arrayMap from 'lodash/_arrayMap';
  2. import property from 'lodash/_baseProperty';
  4. import map from './map';
  5. import wrapAsync from './internal/wrapAsync';
  7. /**
  8.  * Sorts a list by the results of running each `coll` value through an async
  9.  * `iteratee`.
  10.  *
  11.  * @name sortBy
  12.  * @static
  13.  * @memberOf module:Collections
  14.  * @method
  15.  * @category Collection
  16.  * @param {Array|Iterable|Object} coll - A collection to iterate over.
  17.  * @param {AsyncFunction} iteratee - An async function to apply to each item in
  18.  * `coll`.
  19.  * The iteratee should complete with a value to use as the sort criteria as
  20.  * its `result`.
  21.  * Invoked with (item, callback).
  22.  * @param {Function} callback - A callback which is called after all the
  23.  * `iteratee` functions have finished, or an error occurs. Results is the items
  24.  * from the original `coll` sorted by the values returned by the `iteratee`
  25.  * calls. Invoked with (err, results).
  26.  * @example
  27.  *
  28.  * async.sortBy(['file1','file2','file3'], function(file, callback) {
  29.  *     fs.stat(file, function(err, stats) {
  30.  *         callback(err, stats.mtime);
  31.  *     });
  32.  * }, function(err, results) {
  33.  *     // results is now the original array of files sorted by
  34.  *     // modified date
  35.  * });
  36.  *
  37.  * // By modifying the callback parameter the
  38.  * // sorting order can be influenced:
  39.  *
  40.  * // ascending order
  41.  * async.sortBy([1,9,3,5], function(x, callback) {
  42.  *     callback(null, x);
  43.  * }, function(err,result) {
  44.  *     // result callback
  45.  * });
  46.  *
  47.  * // descending order
  48.  * async.sortBy([1,9,3,5], function(x, callback) {
  49.  *     callback(null, x*-1);    //<- x*-1 instead of x, turns the order around
  50.  * }, function(err,result) {
  51.  *     // result callback
  52.  * });
  53.  */
  54. export default function sortBy (coll, iteratee, callback) {
  55.     var _iteratee = wrapAsync(iteratee);
  56.     map(coll, function (x, callback) {
  57.         _iteratee(x, function (err, criteria) {
  58.             if (err) return callback(err);
  59.             callback(null, {value: x, criteria: criteria});
  60.         });
  61.     }, function (err, results) {
  62.         if (err) return callback(err);
  63.         callback(null, arrayMap(results.sort(comparator), property('value')));
  64.     });
  66.     function comparator(left, right) {
  67.         var a = left.criteria, b = right.criteria;
  68.         return a < b ? -1 : a > b ? 1 : 0;
  69.     }
  70. }