FileSystemFileEntry: file() method

{{APIRef("File and Directory Entries API")}}

The {{domxref("FileSystemFileEntry")}} interface's method file() returns a {{domxref("File")}} object which can be used to read data from the file represented by the directory entry.

Syntax

file(successCallback)
file(successCallback, errorCallback)

Parameters

• successCallback
  • : A callback function which is called when the {{domxref("File")}} has been created successfully; the File is passed into the callback as the only parameter.
• errorCallback {{optional_inline}}
  • : If provided, this must be a method which is called when an error occurs while trying to create the {{domxref("File")}}. This callback receives as input a {{domxref("DOMException")}} object describing the error.

Return value

None ({{jsxref("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.

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 {{domxref("FileReader")}} to read the file as text. The FileReader's {{domxref("FileReader/load_event", "load")}} event handler is set up to deliver the loaded string to the successCallback specified when the readFile() method was called; similarly, its {{domxref("FileReader/error_event", "error")}} handler is set up to call the errorCallback specified.

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• File and Directory Entries API