FileSystemFileEntry.file()

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; the File 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 a FileError object describing the error.

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

Return value

undefined.

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

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
fileChrome Full support 8Edge Full support 79Firefox Full support 50IE No support NoOpera No support NoSafari Full support 11.1WebView Android Full support ≤37Chrome Android Full support 18Firefox Android Full support 50Opera Android No support NoSafari iOS Full support 11.3Samsung Internet Android Full support 1.0

Legend

Full support  
Full support
No support  
No support

See also