async/sortBy.js

'use strict';

Object.defineProperty(exports, "__esModule", {
    value: true
});

var _map = require('./map');

var _map2 = _interopRequireDefault(_map);

var _wrapAsync = require('./internal/wrapAsync');

var _wrapAsync2 = _interopRequireDefault(_wrapAsync);

var _awaitify = require('./internal/awaitify');

var _awaitify2 = _interopRequireDefault(_awaitify);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

/**
 * Sorts a list by the results of running each `coll` value through an async
 * `iteratee`.
 *
 * @name sortBy
 * @static
 * @memberOf module:Collections
 * @method
 * @category Collection
 * @param {Array|Iterable|AsyncIterable|Object} coll - A collection to iterate over.
 * @param {AsyncFunction} iteratee - An async function to apply to each item in
 * `coll`.
 * The iteratee should complete with a value to use as the sort criteria as
 * its `result`.
 * Invoked with (item, callback).
 * @param {Function} callback - A callback which is called after all the
 * `iteratee` functions have finished, or an error occurs. Results is the items
 * from the original `coll` sorted by the values returned by the `iteratee`
 * calls. Invoked with (err, results).
 * @returns {Promise} a promise, if no callback passed
 * @example
 *
 * async.sortBy(['file1','file2','file3'], function(file, callback) {
 *     fs.stat(file, function(err, stats) {
 *         callback(err, stats.mtime);
 *     });
 * }, function(err, results) {
 *     // results is now the original array of files sorted by
 *     // modified date
 * });
 *
 * // By modifying the callback parameter the
 * // sorting order can be influenced:
 *
 * // ascending order
 * async.sortBy([1,9,3,5], function(x, callback) {
 *     callback(null, x);
 * }, function(err,result) {
 *     // result callback
 * });
 *
 * // descending order
 * async.sortBy([1,9,3,5], function(x, callback) {
 *     callback(null, x*-1);    //<- x*-1 instead of x, turns the order around
 * }, function(err,result) {
 *     // result callback
 * });
 */
function sortBy(coll, iteratee, callback) {
    var _iteratee = (0, _wrapAsync2.default)(iteratee);
    return (0, _map2.default)(coll, (x, iterCb) => {
        _iteratee(x, (err, criteria) => {
            if (err) return iterCb(err);
            iterCb(err, { value: x, criteria });
        });
    }, (err, results) => {
        if (err) return callback(err);
        callback(null, results.sort(comparator).map(v => v.value));
    });

    function comparator(left, right) {
        var a = left.criteria,
            b = right.criteria;
        return a < b ? -1 : a > b ? 1 : 0;
    }
}
exports.default = (0, _awaitify2.default)(sortBy, 3);
module.exports = exports['default'];