The DirectoryReaderSync interface of the File System API lets you read the entries in a directory.
About this document
This document was last updated on March 2, 2012 and follows the W3C Specifications (Working Draft) drafted on April 19, 2011.
Basic concepts
Before you call the only method in this interface, readEntries(), create the DirectoryEntrySync object. But DirectoryEntrySync (as well as FileEntrySync) is not a data type that you can pass between a calling app and Web Worker thread. It's not a big deal, because you don't really need to have the main app and the worker thread see the same JavaScript object; you just need them to access the same files. You can do that by passing a list of filesystem: URLs—which are just strings—instead of a list of entries. You can also use the filesystem: URL to look up the entry with resolveLocalFileSystemURL(). That gets you back to a DirectoryEntrySync (as well as FileEntrySync) object.
Example
In the following code snippet from HTML5Rocks, we create Web Workers and pass data from it to the main app.
// Taking care of the browser-specific prefixes.
window.resolveLocalFileSystemURL = window.resolveLocalFileSystemURL ||
window.webkitResolveLocalFileSystemURL;
// Create web workers
var worker = new Worker('worker.js');
worker.onmessage = function(e) {
var urls = e.data.entries;
urls.forEach(function(url, i) {
window.resolveLocalFileSystemURL(url, function(fileEntry) {
// Print out file's name.
console.log(fileEntry.name);
});
});
};
worker.postMessage({'cmd': 'list'});
The following is Worker.js code that gets the contents of the directory.
// Taking care of the browser-specific prefixes.
self.requestFileSystemSync = self.webkitRequestFileSystemSync ||
self.requestFileSystemSync;
// Global for holding the list of entry file system URLs.
var paths = [];
function getAllEntries(dirReader) {
var entries = dirReader.readEntries();
for (var i = 0, entry; entry = entries[i]; ++i) {
// Stash this entry's filesystem in URL
paths.push(entry.toURL());
// If this is a directory, traverse.
if (entry.isDirectory) {
getAllEntries(entry.createReader());
}
}
}
// Forward the error to main app.
function onError(e) {
postMessage('ERROR: ' + e.toString());
}
self.onmessage = function(e) {
var data = e.data;
// Ignore everything else except our 'list' command.
if (!data.cmd || data.cmd != 'list') {
return;
}
try {
var fs = requestFileSystemSync(TEMPORARY, 1024*1024 /*1MB*/);
getAllEntries(fs.root.createReader());
self.postMessage({entries: paths});
} catch (e) {
onError(e);
}
};
Method overview
EntrySync readEntries () raises (FileException); |
Method
readEntries()
Returns a lost of entries from a specific directory. Call this method until an empty array is returned.
EntrySync readEntries ( ) raises (FileException);
Returns
Parameter
None
Exceptions
This method can raise a FileException with the following codes:
| Exception | Description |
|---|---|
NOT_FOUND_ERR | The directory does not exist. |
INVALID_STATE_ERR | The directory has been modified since the first call to readEntries was processed. |
SECURITY_ERR | The browser determined that it was not safe to look up the metadata. |
Browser compatibility
{{ CompatibilityTable() }}
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
|---|---|---|---|---|---|
| Basic support | 13{{ property_prefix("webkit") }} | {{ CompatNo() }} | {{ CompatNo() }} | {{ CompatNo() }} | {{ CompatNo() }} |
| Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Phone | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|
| Basic support | {{ CompatNo() }} | 0.16 {{ property_prefix("webkit") }} | {{ CompatNo() }} | {{ CompatNo() }} | {{ CompatNo() }} | {{ CompatNo() }} |
See also
Specification: {{ spec("https://dev.w3.org/2009/dap/file-system/pub/FileSystem/", "File API: Directories and System Specification", "WD") }}
Reference: File System API
Introduction: Basic Concepts About the File System API