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import map from './map';
import wrapAsync from './internal/wrapAsync';
import awaitify from './internal/awaitify'
/**
* 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 = wrapAsync(iteratee);
return map(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;
}
}
export default awaitify(sortBy, 3)
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