FileSystemFileEntry.file()

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范例
规范
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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。

FileSystemFileEntry 接口方法 file () 返回 File object which can be used to read data from the file represented by the directory entry.

句法

FileSystemFileEntry.file(successCallback[, errorCallback]);

参数

successCallback: A callback function which is called when the File has been created successfully; the File is passed into the callback as the only parameter.
errorCallback 可选: If provided, this must be a method which is called when an error occurs while trying to create the File . This callback receives as input a FileError object describing the error.

Editor's note: We need to find out what kinds of errors can occur and document them.

返回值

undefined .

范例

此例子建立方法， readFile() , reads a text file and calls a specified callback function with the received text (in a 字符串 object) once the read is completed. If an error occurs, a specified (optional) error callback is called.

function readFile(entry, successCallback, errorCallback) {
  entry.file(function(file) {
    let reader = new FileReader();
    reader.onload = function() {
      successCallback(reader.result);
    };
    reader.onerror = function() {
      errorCallback(reader.error);
    }
    reader.readAsText(file);
  }, errorCallback);
}

此函数调用 file() , specifying as its success callback a method which proceeds to use a FileReader to read the file as text. The FileReader's load event handler is set up to deliver the loaded string to the successCallback specified when the readFile() method was called; similarly, its error handler is set up to call the errorCallback 指定。

规范

规范	状态	注释
文件和目录条目 API The definition of 'file()' 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
`file`	Chrome 8	Edge 79	Firefox 50	IE No	Opera No	Safari 11.1	WebView Android ≤37	Chrome Android 18	Firefox Android 50	Opera Android No	Safari iOS 11.3	Samsung Internet Android Yes

图例

完整支持
不支持

另请参阅

元数据

最后修改： Dec 25, 2019

文件和目录条目 API
FileSystemFileEntry
方法
1. ~~createWriter()~~
2. file()
文件系统 API 相关页面

在此页

句法

参数

返回值

范例

规范

浏览器兼容性

图例

另请参阅

相关话题