Recursively retrieve directory contents of a specified directory.

chrome-apps-recurseDirectory.js

/**
 * Recursively retrieves the contents of the specified DirectoryEntry.  All
 * entries are appended to an array assigned to the `entries` key of each
 * DirectoryEntry.
 * @param  {!DirectoryEntry} dirEntry  The DirectoryEntry representing the root
 *     directory for which all entries should be retrieved recursively.
 * @param  {function(Array.<DirectoryEntry,FileEntry>)} callback  Function
 *     called after all descendant directories have been traversed.
 */
function recurseDirectory(dirEntry, callback) {
    var dirsLeft = 1;
    var rootEntries;
    function helper(dirEntry, isRoot) {
        dirEntry.createReader().readEntries(function(entries) {
            dirsLeft--;
            if (isRoot) {
                rootEntries = entries;
            }
            (dirEntry.entries = entries).forEach(function(entry) {
                if (entry.isDirectory) {
                    dirsLeft++;
                    helper(entry);
                }
            });
            if (!dirsLeft) {
                callback(rootEntries);
            }
        });
    }
    helper(dirEntry, true);
}