递归自调用函数和异步操作

Question

From this question , I gathered that I could use either a forEach loop or a self-invoked to perform asynchronous I/O operations. I'm not sure why it isn't working for me, but the loop part of things work properly without any asynchronous function being called.

var fileNames = ["fileA", "fileB", "fileC", "fileD", "fileE", "fileF", "fileG", "fileH"];
var json;

(function parseFiles(i) {

    console.log(i + " " + fileNames[i]);

    var uri = new Windows.Foundation.Uri('ms-appx:///data/' + fileNames[i] + '.json');

    Windows.Storage.StorageFile.getFileFromApplicationUriAsync(uri).then(function (file) {
        Windows.Storage.FileIO.readTextAsync(file).then(function (contents) {
            json[fileNames[i]] = JSON.parse(contents);

            if (i < fileNames.length) {
                parseFiles(i+1);
            } else {}
        });
    });

})(0);

My console output is kind of strange:

0 fileA
1 fileB
0 fileA
2 fileC
1 fileB
3 fileD
2 fileC
3 fileD

Two questions here:

1. How do I fix it so that it goes from fileA to fileH?
2. After parsing the files, do I put the code to work with the variable json after the self-invoked function or in the else loop in the then function of the Promise returned by readFileAsync() ?

Answer 1

I ended up doing this:

var fileNames = ["fileA", "fileB", "fileC", "fileD", "fileE", "fileF", "fileG", "fileH"];
var json;

(function parseFiles() {

    var name = fileNames.pop();

    Windows.Storage.StorageFile.getFileFromApplicationUriAsync(new Windows.Foundation.Uri('ms-appx:///data/' + name + '.json'))
        .then(function (file) {
            return Windows.Storage.FileIO.readTextAsync(file);
        }, function error(e){
            console.dir(e);
        })
        .then(function (contents) {
            json[name] = JSON.parse(contents);
        })
        .then(function () {
            console.log("Name: "+name+" Remaining array length:"+fileNames.length);

            if (fileNames.length === 0) {
                console.log('all done');
                // do whatever else here
            } else {
                parseFiles();
            }
        });
})();

I'm just glad that the asynchronous methods in the recursive function use the Promise interface so I don't have to write a whole bunch of recursive functions.