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  3. FileSystemDirectoryEntry
  4. FileSystemDirectoryEntry.getFile()

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这是 实验性技术
检查 浏览器兼容性表格 要小心谨慎在生产中使用这之前。

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FileSystemDirectoryEntry 接口方法 getFile () 返回 FileSystemFileEntry object corresponding to a file contained somewhere within the directory subtree rooted at the directory on which it's called.

句法 

FileSystemDirectoryEntry.getFile([path][, options][, successCallback][, errorCallback]);

参数

path 可选
USVString specifying the path, relative to the directory on which the method is called, describing which file's entry to return.
选项 可选
An object based on the FileSystemFlags dictionary, which allows you to specify whether or not to create the entry if it's missing and if it's an error if the file already exists. These options are currently not useful in Web contexts.
successCallback 可选
A method to be called once the FileSystemFileEntry has been created. The method receives a single parameter: the FileSystemFileEntry object representing the file in question.
errorCallback 可选
A method to be called if an error occurs. Receives as its sole input parameter a FileError object describing the error which occurred.

返回值

undefined .

错误

If an error occurs and an errorCallback was specified, it gets called with a single parameter: a FileError object describing the error. The {domxref("FileError.code")}} specifies what type of error occurred, as follows:

FileError.NOT_FOUND_ERR
create option was not specified (or was specified as false ), and the file doesn't exist.
FileError.PATH_EXISTS_ERR
create and exclusive options were both true , indicating that the file should be created but must not already exist, but the file does in fact already exist.
FileError.SECURITY_ERR

The request to access the file was denied for security reasons.

FileError.TYPE_MISMATCH_ERR

The path specified is not a file; it's probably a directory, but might be an unsupported file descriptor such as a pipe; this depends on the user agent to some extent.

FileSystemFlags

选项 parameter is an object which is based on the FileSystemFlags dictionary; it provides flags which make it possible to adjust the behavior of the getFile() 方法。

create 可选
若此特性为 true , and the requested file or directory doesn't exist, the user agent should create it. The default is false . The parent directory must already exist.
exclusive 可选
若 true ，和 create option is also true , the file must not exist prior to issuing the call. Instead, it must be possible for it to be created newly at call time. The default is false .

Values and results

The table below describes the result of each possible combination of these flags depending on whether or not the target file or directory path already exists.

Option values File/directory condition 结果
create exclusive
false n/a [1] Path exists and matches the desired type (depending on whether the function called is getFile() or getDirectory() successCallback is called with a FileSystemFileEntry if getFile() was called or a FileSystemDirectoryEntry if getDirectory() 被调用。
false n/a [1] Path exists but doesn't match the desired type errorCallback is called with an appropriate error code (if the callback was provided).
true false Path exists The existing file or directory is removed and replaced with a new one, then the successCallback is called with a FileSystemFileEntry 或 FileSystemDirectoryEntry , as appropriate.
true false Path doesn't exist The file or directory is created, then a FileSystemFileEntry 或 FileSystemDirectoryEntry 被传递给 successCallback , as appropriate.
true true Path exists errorCallback is called with an appropriate error, such as FileError.PATH_EXISTS_ERR .
true true Path doesn't exist The file or directory is created, then a FileSystemFileEntry 或 FileSystemDirectoryEntry 被传递给 successCallback , as appropriate.

[1] When create is false ，值对于 exclusive is irrelevant and ignored.

范例

In this example, a function is presented whose job it is to locate within a user's app data directory a JSON file containing a user dictionary for a specified language, then load that dictionary. 

let dictionary = null;
function loadDictionaryForLanguage(appDataDirEntry, lang) {
  dictionary = null;
  appDataDirEntry.getDirectory("Dictionaries", {}, function(dirEntry) {
    dirEntry.getFile(lang + "-dict.json", {}, function(fileEntry) {
      fileEntry.file(function(dictFile)) {
        let reader = new FileReader();
        reader.addEventListener("loadend", function() {
          dictionary = JSON.parse(reader.result);
        });
        reader.readAsText(dictFile);
      });
    });
  });
}

loadDictionaryForLanguage() function starts by using getDirectory() to obtain the FileSystemDirectoryEntry object representing a subfolder named "Dictionaries" located inside the specified app data directory. The success callback for this takes the resulting directory entry object and calls getFile() to get a FileSystemFileEntry object representing the dictionary file; the success callback for this, in turn, creates a new FileReader and uses it to load the contents of the file. When that is loaded successfully (as indicated by the loadend event being fired), the loaded text is passed into JSON.parse() to be reconstituted into a JavaScript object.

规范

规范 状态 注释
文件和目录条目 API
The definition of 'getFile()' in that specification. 		草案 最初的规范。

浏览器兼容性

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. 更新 GitHub 上的兼容性数据
桌面 移动
Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
getFile Chrome 8 Edge 79 Firefox 50
50
In Firefox, the errorCallback 's input parameter is a DOMException 而不是 FileError 对象。
IE No Opera No Safari 11.1 WebView Android ≤37 Chrome Android 18 Firefox Android 50
50
In Firefox, the errorCallback 's input parameter is a DOMException 而不是 FileError 对象。
Opera Android No Safari iOS 11.3 Samsung Internet Android Yes

图例

完整支持

完整支持

不支持

不支持

实验。期望将来行为有所改变。

实验。期望将来行为有所改变。

见实现注意事项。

另请参阅

元数据

  • 最后修改：
  1. 文件和目录条目 API
  2. FileSystemDirectoryEntry
  3. 方法
    1. createReader()
    2. getDirectory()
    3. getFile()
    4. removeRecursively()
  4. 文件系统 API 相关页面
    1. FileError
    2. FileException
    3. FileHandle
    4. FileRequest
    5. FileSystem
    6. FileSystemDirectoryEntrySync
    7. FileSystemDirectoryReader
    8. FileSystemDirectoryReaderSync
    9. FileSystemEntry
    10. FileSystemEntrySync
    11. FileSystemFileEntry
    12. FileSystemFileEntrySync
    13. FileSystemFlags
    14. FileSystemSync
    15. HTMLInputElement
    16. LocalFileSystem
    17. LocalFileSystemSync
    18. LockedFile
    19. 元数据
    20. Window.requestFileSystem()
    21. Window.resolveLocalFileSystemURL()
    22. WorkerGlobalScope.requestFileSystemSync()