Non-standard This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
The DirectoryReaderSync
interface of the File System API lets you read the entries in a directory.
This interface has been abandonned: it was on a standard track and it proves not a good idea. Do not use it anymore.
About this document
This document was last updated on March 2, 2012 and follows the W3C Specifications (Working Draft) drafted on April 19, 2011.
This specification is pretty much abandoned, having failed to reach any substantial traction.
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
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Update compatibility data on GitHub
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Chrome Full support 13 Full support 13 Prefixed' Implemented with the vendor prefix: webkit |
Edge Full support 79 Full support 79 Prefixed' Implemented with the vendor prefix: webkit |
Firefox
No support No |
IE
No support No |
Opera
No support No |
Safari
No support No |
WebView Android Full support 37 Full support 37 Prefixed' Implemented with the vendor prefix: webkit |
Chrome Android Full support 18 Full support 18 Prefixed' Implemented with the vendor prefix: webkit |
Firefox Android
No support No |
Opera Android
No support No |
Safari iOS
No support No |
Samsung Internet Android Full support 1.0 Full support 1.0 Prefixed' Implemented with the vendor prefix: webkit |
Legend
- Full support
- Full support
- No support
- No support
- Non-standard. Expect poor cross-browser support.'
- Non-standard. Expect poor cross-browser support.
- Requires a vendor prefix or different name for use.'
- Requires a vendor prefix or different name for use.
See also
Specification: File API: Directories and System SpecificationWD
Reference: File System API
Introduction: Basic Concepts About the File System API
DirectoryReaderSync by Mozilla Contributors is licensed under CC-BY-SA 2.5.