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FileSystemFileEntry: file() method

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

js

file(successCallback)
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 DOMException object describing the error.

Return value

None (undefined).

Examples

This example establishes a method, readFile(), reads a text file and calls a specified callback function with the received text (in a string) once the read is completed. If an error occurs, a specified (optional) error callback is called.

js

function readFile(entry, successCallback, errorCallback) {
  entry.file((file) => {
    let reader = new FileReader();

    reader.onload = () => {
      successCallback(reader.result);
    };

    reader.onerror = () => {
      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

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
file 8 79 50 No No 11.1 ≤37 18 50 14 11.3 1.0

See also

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https://developer.mozilla.org/en-US/docs/Web/API/FileSystemFileEntry/file