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.

This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

In the 文件系统 API FileException object represents error conditions that you might encounter while accessing the file system using the synchronous API. It extends the FileException interface described in File Writer and adds several new error codes.


Synchronous APIs do not have error callbacks, which makes it difficult to catch errors. The added complexity of using WebWorkers with this API makes debugging even more challenging. To simplify things a bit, wrap your worker code in a try/catch. When errors occur, forward them to the main app using postMessage() as in the following:

function onError(e) {
  postMEssage('ERROR:' + e.toString());
try {
  //Error is thrown if "log.txt" already exists.
var fileEntry = fs.root.getFile('log.txt', {create: true, exclusive:true}0;
} catch (e) {

The sample code was borrowed from HTML5Rocks


属性 Type 描述
code unsigned short The most appropriate error code for the condition.


注意: Do not rely on the numeric values of the constants, which might change as the specifications continue to change. Use the constant names instead.
常量 描述
ENCODING_ERR 5 The URL is malformed. Make sure that the URL is complete and valid.
INVALID_MODIFICATION_ERR 9 The modification requested is not allowed. Examples of invalid modifications include moving a directory into its own child or moving a file into its parent directory without changing its name.
INVALID_STATE_ERR 7 The operation cannot be performed on the current state of the interface object. For example, the state that was cached in an interface object has changed since it was last read from disk.
NO_MODIFICATION_ALLOWED_ERR 6 The state of the underlying file system prevents any writing to a file or a directory.
NOT_FOUND_ERR 1 A required file or directory could not be found at the time an operation was processed. For example, a file did not exist but was being opened.

The file or directory cannot be read, typically due to permission problems that occur after a reference to a file has been acquired (for example, the file or directory is concurrently locked by another application).

PATH_EXISTS_ERR 12 The file or directory with the same path already exists.

Either there's not enough remaining storage space or the storage quota was reached and the user declined to give more space to the database.


Access to the files were denied for one of the following reasons:

  • The files might be unsafe for access within a Web application.
  • Too many calls are being made on file resources.
  • Other unspecified security error code or situations.
TYPE_MISMATCH_ERR 11 The user has attempted to look up a file or directory, but the Entry found is of the wrong type. For example, the app is accessing a DirectoryEntry when the user is requesting a FileEntry.


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
弃用 非标
Chrome 13 — 29
不支持 13 — 29
Prefixed Implemented with the vendor prefix: webkit
Edge No Firefox No IE No Opera No Safari No WebView Android No Chrome Android 18 — 29
不支持 18 — 29
Prefixed Implemented with the vendor prefix: webkit
Firefox Android No Opera Android No Safari iOS No Samsung Internet Android 1.0 — 3.0
不支持 1.0 — 3.0
Prefixed Implemented with the vendor prefix: webkit




Specification: File API: Directories and System Specification WD

Reference: 文件系统 API

Introduction: Basic Concepts About the File System API