license: Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

     Unless required by applicable law or agreed to in writing,
     software distributed under the License is distributed on an
     "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
     KIND, either express or implied.  See the License for the
     specific language governing permissions and limitations
     under the License.

FileReader

The FileReader allows basic access to a file.

Properties

readyState: One of the reader's three possible states, either EMPTY, LOADING or DONE.
result: The contents of the file that have been read. (DOMString)
error: An object containing errors. (FileError)
onloadstart: Called when the read starts. (Function)
onload: Called when the read has successfully completed. (Function)
onabort: Called when the read has been aborted. For instance, by invoking the abort() method. (Function)
onerror: Called when the read has failed. (Function)
onloadend: Called when the request has completed (either in success or failure). (Function)

NOTE: The following porperty is not supported:

onprogress: Called while reading the file, reporting progress in terms of progress.loaded/progress.total. (Function)

Methods

abort: Aborts reading file.
readAsDataURL: Read file and return data as a base64-encoded data URL.
readAsText: Reads text file.
readAsBinaryString: Reads file as binary and returns a binary string.
readAsArrayBuffer: Reads file as an ArrayBuffer.

Details

The FileReader object offers a way to read files from the device's file system. Files can be read as text or as a base64 data-encoded string. Event listeners receive the loadstart, progress, load, loadend, error, and abort events.

Supported Platforms

Amazon Fire OS
Android
BlackBerry WebWorks 5.0+
iOS
Windows Phone 7 and 8
Windows 8

readAsDataURL

Parameters:

file: the file object to read.

Quick Example

function win(file) {
    var reader = new FileReader();
    reader.onloadend = function (evt) {
        console.log("read success");
        console.log(evt.target.result);
    };
    reader.readAsDataURL(file);
};

var fail = function (error) {
    console.log(error.code);
};

entry.file(win, fail);

readAsText

Parameters:

file: the file object to read.
encoding: the encoding to use to encode the file's content. Default is UTF8.

Quick Example

function win(file) {
    var reader = new FileReader();
    reader.onloadend = function (evt) {
        console.log("read success");
        console.log(evt.target.result);
    };
    reader.readAsText(file);
};

var fail = function (error) {
    console.log(error.code);
};

entry.file(win, fail);

abort

function win(file) {
    var reader = new FileReader();
    reader.onloadend = function(evt) {
        console.log("read success");
        console.log(evt.target.result);
    };
    reader.readAsText(file);
    reader.abort();
};

function fail(error) {
    console.log(error.code);
}

entry.file(win, fail);

Full Example

<!DOCTYPE html>
<html>
  <head>
    <title>FileReader Example</title>

    <script type="text/javascript" charset="utf-8" src="cordova.js"></script>
    <script type="text/javascript" charset="utf-8">

    // Wait for device API libraries to load
    //
    document.addEventListener("deviceready", onDeviceReady, false);

    // device APIs are available
    //
    function onDeviceReady() {
        window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, gotFS, fail);
    }

    function gotFS(fileSystem) {
        fileSystem.root.getFile("readme.txt", null, gotFileEntry, fail);
    }

    function gotFileEntry(fileEntry) {
        fileEntry.file(gotFile, fail);
    }

    function gotFile(file){
        readDataUrl(file);
        readAsText(file);
    }

    function readDataUrl(file) {
        var reader = new FileReader();
        reader.onloadend = function(evt) {
            console.log("Read as data URL");
            console.log(evt.target.result);
        };
        reader.readAsDataURL(file);
    }

    function readAsText(file) {
        var reader = new FileReader();
        reader.onloadend = function(evt) {
            console.log("Read as text");
            console.log(evt.target.result);
        };
        reader.readAsText(file);
    }

    function fail(error) {
        console.log(error.code);
    }

    </script>
  </head>
  <body>
    <h1>Example</h1>
    <p>Read File</p>
  </body>
</html>

iOS Quirks

The encoding parameter is not supported, and UTF8 encoding is always in effect.

readAsBinaryString

Currently supported on iOS and Android only.

Parameters:

file: the file object to read.

Quick Example

function win(file) {
    var reader = new FileReader();
    reader.onloadend = function (evt) {
        console.log("read success");
        console.log(evt.target.result);
    };
    reader.readAsBinaryString(file);
};

var fail = function (error) {
    console.log(error.code);
};

entry.file(win, fail);

readAsArrayBuffer

Currently supported on iOS and Android only.

Parameters:

file: the file object to read.

Quick Example

function win(file) {
    var reader = new FileReader();
    reader.onloadend = function (evt) {
        console.log("read success");
        console.log(new Uint8Array(evt.target.result));
    };
    reader.readAsArrayBuffer(file);
};

var fail = function (error) {
    console.log(error.code);
};

entry.file(win, fail);