This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
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 called 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. |
Draft | Initial specification. |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
file | Chrome Full support 8 | Edge Full support 79 | Firefox Full support 50 | IE No support No | Opera No support No | Safari Full support 11.1 | WebView Android Full support ≤37 | Chrome Android Full support 18 | Firefox Android Full support 50 | Opera Android No support No | Safari iOS Full support 11.3 | Samsung Internet Android Full support Yes |
Legend
- Full support
- Full support
- No support
- No support