Web/API/FileSystemFileEntry/file

This is an experimental technologyCheck 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 APIThe definition of 'file()' in that specification.	Draft	Initial specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	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 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 1.0

Legend

Full support: Full support
No support: No support