FileSystemFileEntry.file()
This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.
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 FileSystemFileEntry
interface's method file
()
returns a File
object which can be used to read data from the file represented by the directory entry.
Syntax
FileSystemFileEntry.file(successCallback[, errorCallback]);
Parameters
successCallback
- A callback function which is called when the
File
has been created successfully; theFile
is passed into the callback as the only parameter. errorCallback
Optional- If provided, this must be a method which is caled when an error occurs while trying to create the
File
. This callback receives as input aFileError
object describing the error.
Editor's note: We need to find out what kinds of errors can occur and document them.
Return value
Example
This example establishes a method, readFile()
, reads a text file and calls a specified callback function with the received text (in a String
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); }
This function calls 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
specified.
Specifications
Specification | Status | Comment |
---|---|---|
File and Directory Entries API The definition of 'file()' in that specification. |
Editor's Draft | Initial specification. |
This API has no official W3C or WHATWG specification.
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 13 webkit | 50 (50) | No support | No support | No support |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Phone | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | No support | 0.16webkit | 50.0 (50) | No support | No support | No support |
See also
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/api/filesystemfileentry/file