node.js - Why async.map function works with the native fs.stat function? -

async.map(['file1','file2','file3'], fs.stat, function(err, results){     // results array of stats each file }); 

as per documentation, second argument is:

iterator(item, callback) - function apply each item in array.

fine.

the iterator passed callback(err, transformed) must called once has completed error (which can null) , transformed item.

i think thatfs.stat not conform , shouldn't work.

it should like:

async.map(['file1','file2','file3'],     function (file, complete) {         fs.stat(file, function (err, stat) {             complete(err, stat)         });     }, function(err, results){         // results array of stats each file     } ); 

fs.stat accepts 2 parameters, first file, second callback, node convention accepts 2 parameters, error , stats of file:

fs.stat(path, callback) 

which seen as

fs.stat(path, function(err, stats){   // ... }); 

this why works, fs.stat called passing needs.

more info: http://nodejs.org/api/fs.html#fs_fs_stat_path_callback