DirectoryReaderSync

非标
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.

DirectoryReaderSync interface of the 文件系统 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.

基本概念

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.

范例

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);
					
返回
Parameter

None

异常

This method can raise a FileException with the following codes:

Exception 描述
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.

浏览器兼容性

更新 GitHub 上的兼容性数据
Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
DirectoryReaderSync
非标
Chrome 13
Prefixed
13
Prefixed
Prefixed Implemented with the vendor prefix: webkit
Edge 79
Prefixed
79
Prefixed
Prefixed Implemented with the vendor prefix: webkit
Firefox No IE No Opera No Safari No WebView Android 37
Prefixed
37
Prefixed
Prefixed Implemented with the vendor prefix: webkit
Chrome Android 18
Prefixed
18
Prefixed
Prefixed Implemented with the vendor prefix: webkit
Firefox Android No Opera Android No Safari iOS No Samsung Internet Android 1.0
Prefixed
1.0
Prefixed
Prefixed Implemented with the vendor prefix: webkit

图例

完整支持
完整支持
不支持
不支持
非标。预期跨浏览器支持较差。
非标。预期跨浏览器支持较差。
要求使用供应商前缀或不同名称。
要求使用供应商前缀或不同名称。

另请参阅

Specification: File API: Directories and System Specification WD

Reference: 文件系统 API

Introduction: Basic Concepts About the File System API