# File Plugin
Tested Version: [7.0.0](https://github.com/apache/cordova-plugin-file/releases/tag/7.0.0)
{% hint style="info" %}
This document is based on the original Cordova docs available at [Cordova Docs](https://github.com/apache/cordova-plugin-file).
{% endhint %}
This plugin implements a File API allowing read/write access to files residing on the device. This plugin is based on several specs, including :
* [The HTML5 File API](http://www.w3.org/TR/FileAPI/)
* [The Directories and System extensions Latest](http://www.w3.org/TR/2012/WD-file-system-api-20120417/)
Although most of the plugin code was written when [an earlier spec](http://www.w3.org/TR/2011/WD-file-system-api-20110419/) was current.
* It also implements the [FileWriter spec](http://dev.w3.org/2009/dap/file-system/file-writer.html)
{% hint style="info" %}
While the W3C FileSystem spec is deprecated for web browsers, the FileSystem APIs are supported in Cordova applications with this plugin for the platforms listed in the **Supported Platforms** list, with the exception of the Browser platform.
{% endhint %}
To get a few ideas how to use the plugin, check out the [sample](https://en.docs.monaca.io/reference/cordova_10.0/file#sample-create-files-and-directories-write-read-and-append-files) at the bottom of this page. For additional examples (browser focused), see the HTML5 Rocks' [FileSystem article.](http://www.html5rocks.com/en/tutorials/file/filesystem/) For an overview of other storage options, refer to Cordova's [storage guide](http://cordova.apache.org/docs/en/latest/cordova/storage/storage.html).
This plugin defines global `cordova.file` object. Although in the global scope, it is not available until after the `deviceready` event.
```javascript
document.addEventListener("deviceready", onDeviceReady, false);
function onDeviceReady() {
console.log(cordova.file);
}
```
## Plugin ID
```javascript
cordova-plugin-file
```
## Adding the Plugin in Monaca
In order to use this plugin, please In order to use this plugin, please [enable](https://en.docs.monaca.io/products_guide/monaca_ide/dependencies/cordova_plugin#import-cordova-plugins) `File` plugin in Monaca Cloud IDE.
## Supported Platforms
* Android
* iOS
## Where to Store Files
As of v1.2.0, URLs to important file-system directories are provided. Each URL is in the form , and can be converted to a `DirectoryEntry` using `window.resolveLocalFileSystemURL()`.
* `cordova.file.applicationDirectory` - Read-only directory where the application is installed. (iOS, Android, BlackBerry 10, OSX, windows)
* `cordova.file.applicationStorageDirectory` - Root directory of the application's sandbox; on iOS & windows this location is read-only (but specific subdirectories \[like `/Documents` on iOS or `/localState` on windows] are read-write). All data contained within is private to the app. (iOS, Android, BlackBerry 10, OSX)
* `cordova.file.dataDirectory` - Persistent and private data storage within the application's sandbox using internal memory (on Android, if you need to use external memory, use `.externalDataDirectory`). On iOS, this directory is not synced with iCloud (use `.syncedDataDirectory`). (iOS, Android, BlackBerry 10, windows)
* `cordova.file.cacheDirectory` - Directory for cached data files or any files that your app can re-create easily. The OS may delete these files when the device runs low on storage, nevertheless, apps should not rely on the OS to delete files in here. (iOS, Android, BlackBerry 10, OSX, windows)
* `cordova.file.externalApplicationStorageDirectory` - Application space on external storage. (Android)
* `cordova.file.externalDataDirectory` - Where to put app-specific data files on external storage. (Android)
* `cordova.file.externalCacheDirectory` - Application cache on external storage. (Android)
* `cordova.file.externalRootDirectory` - External storage (SD card) root. (Android, BlackBerry 10)
* `cordova.file.tempDirectory` - Temp directory that the OS can clear at will. Do not rely on the OS to clear this directory; your app should always remove files as applicable. (iOS, OSX, windows)
* `cordova.file.syncedDataDirectory` - Holds app-specific files that should be synced (e.g. to iCloud). (iOS, windows)
* `cordova.file.documentsDirectory` - Files private to the app, but that are meaningful to other application (e.g. Office files). Note that for *OSX* this is the user's `~/Documents` directory. (iOS, OSX)
* `cordova.file.sharedDirectory` - Files globally available to all applications (BlackBerry 10)
## File System Layouts
Although technically an implementation detail, it can be very useful to know how the `cordova.file.*` properties map to physical paths on a real device.
### iOS File System Layout
| Device Path | cordova.file.\* | iosExtraFileSystems | r/w | persistent | OS clears | sync | private |
| ---------------------------------- | --------------------------- | ------------------- | --- | ---------- | --------- | ---- | ------- |
| `/var/mobile/Applications//` | applicationStorageDirectory | | r | N/A | N/A | N/A | Yes |
| `appname.app/` | applicationDirectory | bundle | r | N/A | N/A | N/A | Yes |
| `www/` | | | r | N/A | N/A | N/A | Yes |
| `Documents/` | documentsDirectory | documents | r/w | Yes | No | Yes | Yes |
| `NoCloud/` | | documents-nosync | r/w | Yes | No | No | Yes |
| `Cloud/` | syncedDataDirectory | | r/w | Yes | No | Yes | Yes |
| `Caches/` | cacheDirectory | cache | r/w | Yes\* | No\*\*\* | No | Yes |
| `tmp/` | tempDirectory | | r/w | No\*\* | Yes\*\*\* | No | Yes |
\* Files persist across app restarts and upgrades, but this directory can be cleared whenever the OS desires. Your app should be able to recreate any content that might be deleted.
\*\* Files may persist across app restarts, but do not rely on this behavior. Files are not guaranteed to persist across updates. Your app should remove files from this directory when it is applicable, as the OS does not guarantee when (or even if) these files are removed.
\*\*\* The OS may clear the contents of this directory whenever it feels it is necessary, but do not rely on this. You should clear this directory as appropriate for your application.
### Android File System Layout
| Device Path | cordova.file.\* | AndroidExtraFileSystems | r/w | persistent | OS clears | private |
| ------------------------ | ----------------------------------- | ----------------------- | --------- | ---------- | --------- | ------- |
| `file:///android_asset/` | applicationDirectory | assets | r | N/A | N/A | Yes |
| `/data/data//` | applicationStorageDirectory | | r/w | N/A | N/A | Yes |
| `cache` | cacheDirectory | cache | r/w | Yes | Yes\* | Yes |
| `files` | dataDirectory | files | r/w | Yes | No | Yes |
| `Documents` | | documents | r/w | Yes | No | Yes |
| `/` | externalRootDirector | sdcard | r/w\*\*\* | Yes | No | No |
| `Android/data//` | externalApplicationStorageDirectory | | r/w | Yes | No | No |
| `cache` | externalCacheDirectory | cache-external | r/w | Yes | No\*\* | No |
| `files` | externalDataDirectory | files-external | r/w | Yes | No | No |
\* The OS may periodically clear this directory, but do not rely on this behavior. Clear the contents of this directory as appropriate for your application. Should a user purge the cache manually, the contents of this directory are removed.
\*\* The OS does not clear this directory automatically; you are responsible for managing the contents yourself. Should the user purge the cache manually, the contents of the directory are removed.
\*\*\* As of API 30, these directories are no longer writable.
{% hint style="info" %}
If external storage can't be mounted, the `cordova.file.external*` properties are `null`.
{% endhint %}
## Quirks
### Android Quirks
#### Android Persistent storage location
There are multiple valid locations to store persistent files on an Android device. See [this page](http://developer.android.com/guide/topics/data/data-storage.html) for an extensive discussion of the various possibilities.
Previous versions of the plugin would choose the location of the temporary and persistent files on startup, based on whether the device claimed that the SD Card (or equivalent storage partition) was mounted. If the SD Card was mounted, or if a large internal storage partition was available (such as on Nexus devices,) then the persistent files would be stored in the root of that space. This meant that all Cordova apps could see all of the files available on the card.
If the SD card was not available, then previous versions would store data under `/data/data/`, which isolates apps from each other, but may still cause data to be shared between users.
It is now possible to choose whether to store files in the internal file storage location, or using the previous logic, with a preference in your application's `config.xml` file. To do this, add one of these two lines to `config.xml`:
```markup
```
Without this line, the File plugin will use `Internal` as the default. If a preference tag is present, and is not one of these values, the application will not start.
If your application has previously been shipped to users, using an older (pre- 3.0.0) version of this plugin, and has stored files in the persistent filesystem, then you should set the preference to `Compatibility` if your config.xml does not specify a location for the persistent filesystem. Switching the location to "Internal" would mean that existing users who upgrade their application may be unable to access their previously-stored files, depending on their device.
If your application is new, or has never previously stored files in the persistent filesystem, then the `Internal` setting is generally recommended.
#### Slow recursive operations for /android\_asset
Listing asset directories is really slow on Android. You can speed it up though, by adding `src/android/build-extras.gradle` to the root of your android project (also requires cordova-android\@4.0.0 or greater).
#### Permission to write to external storage when it's not mounted on Marshmallow
Marshmallow requires the apps to ask for permissions when reading/writing to external locations. By [default](http://developer.android.com/guide/topics/data/data-storage.html#filesExternal), your app has permission to write to `cordova.file.applicationStorageDirectory` and `cordova.file.externalApplicationStorageDirectory`, and the plugin doesn't request permission for these two directories unless external storage is not mounted. However due to a limitation, when external storage is not mounted, it would ask for permission to write to `cordova.file.externalApplicationStorageDirectory`.
### iOS Quirks
* `cordova.file.applicationStorageDirectory` is read-only; attempting to store files within the root directory will fail. Use one of the other `cordova.file.*` properties defined for iOS (only `applicationDirectory` and `applicationStorageDirectory` are read-only).
* `FileReader.readAsText(blob, encoding)`
* The `encoding` parameter is not supported, and UTF-8 encoding is always in effect.
#### iOS Persistent storage location
There are two valid locations to store persistent files on an iOS device: the Documents directory and the Library directory. Previous versions of the plugin only ever stored persistent files in the Documents directory. This had the side-effect of making all of an application's files visible in iTunes, which was often unintended, especially for applications which handle lots of small files, rather than producing complete documents for export, which is the intended purpose of the directory.
It is now possible to choose whether to store files in the documents or library directory, with a preference in your application's `config.xml` file. To do this, add one of these two lines to `config.xml`:
```markup
```
Without this line, the File plugin will use `Compatibility` as the default. If a preference tag is present, and is not one of these values, the application will not start.
If your application has previously been shipped to users, using an older (pre- 1.0) version of this plugin, and has stored files in the persistent filesystem, then you should set the preference to `Compatibility`. Switching the location to `Library` would mean that existing users who upgrade their application would be unable to access their previously-stored files.
If your application is new, or has never previously stored files in the persistent filesystem, then the `Library` setting is generally recommended.
## Upgrading Notes
In v1.0.0 of this plugin, the `FileEntry` and `DirectoryEntry` structures have changed, to be more in line with the published specification.
Previous (pre-1.0.0) versions of the plugin stored the device-absolute-file-location in the `fullPath` property of `Entry` objects. These paths would typically look like
```bash
/var/mobile/Applications//Documents/path/to/file (iOS)
/storage/emulated/0/path/to/file (Android)
```
These paths were also returned by the `toURL()` method of the `Entry` objects.
With v1.0.0, the `fullPath` attribute is the path to the file, *relative to the root of the HTML filesystem*. So, the above paths would now both be represented by a `FileEntry` object with a `fullPath` of
```bash
/path/to/file
```
If your application works with device-absolute-paths, and you previously retrieved those paths through the `fullPath` property of `Entry` objects, then you should update your code to use `entry.toURL()` instead.
For backwards compatibility, the `resolveLocalFileSystemURL()` method will accept a device-absolute-path, and will return an `Entry` object corresponding to it, as long as that file exists within either the `TEMPORARY` or `PERSISTENT` filesystems.
This has particularly been an issue with the File-Transfer plugin, which previously used device-absolute-paths (and can still accept them). It has been updated to work correctly with FileSystem URLs, so replacing `entry.fullPath` with `entry.toURL()` should resolve any issues getting that plugin to work with files on the device.
In v1.1.0 the return value of `toURL()` was changed (see [CB-6394](https://issues.apache.org/jira/browse/CB-6394)) to return an absolute '[file://](file:///)' URL. wherever possible. To ensure a 'cdvfile:'-URL you can use `toInternalURL()` now. This method will now return filesystem URLs of the form
```bash
cdvfile://localhost/persistent/path/to/file
```
which can be used to identify the file uniquely.
In v7.0.0 the return value of `toURL()` for Android was updated to return the absolute `file://` URL when app content is served from the `file://` scheme.
If app content is served from the `http(s)://` scheme, a `cdvfile` formatted URL will be returned instead. The `cdvfile` formatted URL is created from the internal method `toInternalURL()`.
An example `toInternalURL()` return filesystem URL:
```
https://localhost/persistent/path/to/file
```
It is recommended to always use the `toURL()` to ensure that the correct URL is returned.
## cdvfile protocol
{% hint style="info" %}
Not Supported on Android
{% endhint %}
### Purpose
`cdvfile://localhost/persistent|temporary|another-fs-root*/path/to/file` can be used for platform-independent file paths. cdvfile paths are supported by core plugins - for example you can download an mp3 file to cdvfile-path via `cordova-plugin-file-transfer` and play it via `cordova-plugin-media`.
{% hint style="info" %}
See [Where to Store Files](https://en.docs.monaca.io/reference/cordova_10.0/file#where-to-store-files), [File System Layouts](https://en.docs.monaca.io/reference/cordova_10.0/file#file-system-layouts) and [Configuring the Plugin](https://en.docs.monaca.io/reference/cordova_10.0/file#configuring-the-plugin-optional) for more details about available fs roots.
{% endhint %}
To use `cdvfile` as a tag' `src` you can convert it to native path via `toURL()` method of the resolved fileEntry, which you can get via `resolveLocalFileSystemURL` - see examples below. You can also use `cdvfile://` paths directly in the DOM, for example:
```markup
```
This method requires following Content Security rules updates:
* Add `cdvfile:` scheme to `Content-Security-Policy` meta tag of the index page, e.g.:
```markup
html
```
* Add `` to `config.xml`.
**Converting cdvfile:// to native path**
```javascript
resolveLocalFileSystemURL('cdvfile://localhost/temporary/path/to/file.mp4', function(entry) {
var nativePath = entry.toURL();
console.log('Native URI: ' + nativePath);
document.getElementById('video').src = nativePath;
}
```
**Converting native path to cdvfile://**
```javascript
resolveLocalFileSystemURL(nativePath, function(entry) {
console.log('cdvfile URI: ' + entry.toInternalURL());
}
```
**Using cdvfile in core plugins**
```javascript
fileTransfer.download(uri, 'cdvfile://localhost/temporary/path/to/file.mp3', function (entry) { ...
```
```javascript
var my_media = new Media('cdvfile://localhost/temporary/path/to/file.mp3', ...);
my_media.play();
```
## List of Error Codes and Meanings
When an error is thrown, one of the following codes will be used.
| Code | Constant |
| ---- | ----------------------------- |
| `1` | `NOT_FOUND_ERR` |
| `2` | `SECURITY_ERR` |
| `3` | `ABORT_ERR` |
| `4` | `NOT_READABLE_ERR` |
| `5` | `ENCODING_ERR` |
| `6` | `NO_MODIFICATION_ALLOWED_ERR` |
| `7` | `INVALID_STATE_ERR` |
| `8` | `SYNTAX_ERR` |
| `9` | `INVALID_MODIFICATION_ERR` |
| `10` | `QUOTA_EXCEEDED_ERR` |
| `11` | `TYPE_MISMATCH_ERR` |
| `12` | `PATH_EXISTS_ERR` |
## Configuring the Plugin (Optional)
The set of available filesystems can be configured per-platform. Both iOS and Android recognize a tag in `config.xml` which names the filesystems to be installed. By default, all file-system roots are enabled.
```markup
```
### Android
* `files`: The application's internal file storage directory
* `files-external`: The application's external file storage directory
* `sdcard`: The global external file storage directory (this is the
root of the SD card, if one is installed). You must have the
`android.permission.WRITE_EXTERNAL_STORAGE` permission to use this.
* `cache`: The application's internal cache directory
* `cache-external`: The application's external cache directory
* `assets`: The application's bundle (read-only)
* `root`: The entire device filesystem
Android also supports a special filesystem named "documents", which represents a "/Documents/" subdirectory within the "files" filesystem.
### iOS
* `library`: The application's Library directory
* `documents`: The application's Documents directory
* `cache`: The application's Cache directory
* `bundle`: The application's bundle; the location of the app itself
on disk (read-only)
* `root`: The entire device filesystem
By default, the library and documents directories can be synced to iCloud. You can also request two additional filesystems, `library-nosync` and `documents-nosync`, which represent a special non-synced directory within the `/Library` or `/Documents` filesystem.
## Sample: Create Files and Directories, Write, Read, and Append files
The File plugin allows you to do things like store files in a temporary or persistent storage location for your app (sandboxed storage) and to store files in other platform-dependent locations. The code snippets in this section demonstrate different tasks including:
* [Accessing the file system](https://en.docs.monaca.io/reference/cordova_10.0/file#create-a-persistent-file)
* Using cross-platform Cordova file URLs to [store your files](https://en.docs.monaca.io/reference/cordova_10.0/file#append-a-file-using-alternative-methods) (see Where to Store Files for more info)
* Creating [files](https://en.docs.monaca.io/reference/cordova_10.0/file#create-a-persistent-file) and [directories](https://en.docs.monaca.io/reference/cordova_10.0/file#create-directories)
* [Writing to files](https://en.docs.monaca.io/reference/cordova_10.0/file#write-to-a-file)
* [Reading files](https://en.docs.monaca.io/reference/cordova_10.0/file#read-a-file)
* [Appending files](https://en.docs.monaca.io/reference/cordova_10.0/file#append-a-file-using-alternative-methods)
* [Display an image file](https://en.docs.monaca.io/reference/cordova_10.0/file#display-an-image-file)
### Create a persistent file
Before you use the File plugin APIs, you can get access to the file system using `requestFileSystem`. When you do this, you can request either persistent or temporary storage. Persistent storage will not be removed unless permission is granted by the user.
When you get file system access using `requestFileSystem`, access is granted for the sandboxed file system only (the sandbox limits access to the app itself), not for general access to any file system location on the device. (To access file system locations outside the sandboxed storage, use other methods such as `window.resolveLocalFileSystemURL`, which support platform-specific locations. For one example of this, see *Append a File*.)
Here is a request for persistent storage.
```javascript
window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function (fs) {
console.log('file system open: ' + fs.name);
fs.root.getFile("newPersistentFile.txt", { create: true, exclusive: false }, function (fileEntry) {
console.log("fileEntry is file?" + fileEntry.isFile.toString());
// fileEntry.name == 'someFile.txt'
// fileEntry.fullPath == '/someFile.txt'
writeFile(fileEntry, null);
}, onErrorCreateFile);
}, onErrorLoadFs);
```
The success callback receives FileSystem object (fs). Use `fs.root` to return a DirectoryEntry object, which you can use to create or get a file (by calling `getFile`). In this example, `fs.root` is a DirectoryEntry object that represents the persistent storage in the sandboxed file system.
The success callback for `getFile` receives a FileEntry object. You can use this to perform file write and file read operations.
### Create a temporary file
Here is an example of a request for temporary storage. Temporary storage may be deleted by the operating system if the device runs low on memory.
```javascript
window.requestFileSystem(window.TEMPORARY, 5 * 1024 * 1024, function (fs) {
console.log('file system open: ' + fs.name);
createFile(fs.root, "newTempFile.txt", false);
}, onErrorLoadFs);
```
When you are using temporary storage, you can create or get the file by calling `getFile`. As in the persistent storage example, this will give you a FileEntry object that you can use for read or write operations.
```javascript
function createFile(dirEntry, fileName, isAppend) {
// Creates a new file or returns the file if it already exists.
dirEntry.getFile(fileName, {create: true, exclusive: false}, function(fileEntry) {
writeFile(fileEntry, null, isAppend);
}, onErrorCreateFile);
}
```
### Write to a file
Once you have a FileEntry object, you can write to the file by calling `createWriter`, which returns a FileWriter object in the success callback. Call the `write` method of FileWriter to write to the file.
```javascript
function writeFile(fileEntry, dataObj) {
// Create a FileWriter object for our FileEntry (log.txt).
fileEntry.createWriter(function (fileWriter) {
fileWriter.onwriteend = function() {
console.log("Successful file write...");
readFile(fileEntry);
};
fileWriter.onerror = function (e) {
console.log("Failed file write: " + e.toString());
};
// If data object is not passed in,
// create a new Blob instead.
if (!dataObj) {
dataObj = new Blob(['some file data'], { type: 'text/plain' });
}
fileWriter.write(dataObj);
});
}
```
### Read a file
You also need a FileEntry object to read an existing file. Use the file property of FileEntry to get the file reference, and then create a new FileReader object. You can use methods like `readAsText` to start the read operation. When the read operation is complete, `this.result` stores the result of the read operation.
```javascript
function readFile(fileEntry) {
fileEntry.file(function (file) {
var reader = new FileReader();
reader.onloadend = function() {
console.log("Successful file read: " + this.result);
displayFileData(fileEntry.fullPath + ": " + this.result);
};
reader.readAsText(file);
}, onErrorReadFile);
}
```
### Append a file using alternative methods
Of course, you will often want to append existing files instead of creating new ones. Here is an example of that. This example shows another way that you can access the file system using window\.resolveLocalFileSystemURL. In this example, pass the cross-platform Cordova file URL, cordova.file.dataDirectory, to the function. The success callback receives a DirectoryEntry object, which you can use to do things like create a file.
```javascript
window.resolveLocalFileSystemURL(cordova.file.dataDirectory, function (dirEntry) {
console.log('file system open: ' + dirEntry.name);
var isAppend = true;
createFile(dirEntry, "fileToAppend.txt", isAppend);
}, onErrorLoadFs);
```
In addition to this usage, you can use `resolveLocalFileSystemURL` to get access to some file system locations that are not part of the sandboxed storage system. See *Where to store Files* for more information; many of these storage locations are platform-specific. You can also pass cross-platform file system locations to `resolveLocalFileSystemURL` using the *cdvfile protocol*.
For the append operation, there is nothing new in the `createFile` function that is called in the preceding code (see the preceding examples for the actual code). `createFile` calls `writeFile`. In `writeFile`, you check whether an append operation is requested.
Once you have a FileWriter object, call the `seek` method, and pass in the index value for the position where you want to write. In this example, you also test whether the file exists. After calling seek, then call the write method of FileWriter.
```javascript
function writeFile(fileEntry, dataObj, isAppend) {
// Create a FileWriter object for our FileEntry (log.txt).
fileEntry.createWriter(function (fileWriter) {
fileWriter.onwriteend = function() {
console.log("Successful file read...");
readFile(fileEntry);
};
fileWriter.onerror = function (e) {
console.log("Failed file read: " + e.toString());
};
// If we are appending data to file, go to the end of the file.
if (isAppend) {
try {
fileWriter.seek(fileWriter.length);
}
catch (e) {
console.log("file doesn't exist!");
}
}
fileWriter.write(dataObj);
});
}
```
### Store an existing binary file
We already showed how to write to a file that you just created in the sandboxed file system. What if you need to get access to an existing file and convert that to something you can store on your device? In this example, you obtain a file using an xhr request, and then save it to the cache in the sandboxed file system.
Before you get the file, get a FileSystem reference using `requestFileSystem`. By passing window\.TEMPORARY in the method call (same as before), the returned FileSystem object (fs) represents the cache in the sandboxed file system. Use `fs.root` to get the DirectoryEntry object that you need.
```javascript
window.requestFileSystem(window.TEMPORARY, 5 * 1024 * 1024, function (fs) {
console.log('file system open: ' + fs.name);
getSampleFile(fs.root);
}, onErrorLoadFs);
```
For completeness, here is the xhr request to get a Blob image. There is nothing Cordova-specific in this code, except that you forward the DirectoryEntry reference that you already obtained as an argument to the saveFile function. You will save the blob image and display it later after reading the file (to validate the operation).
```javascript
function getSampleFile(dirEntry) {
var xhr = new XMLHttpRequest();
xhr.open('GET', 'http://cordova.apache.org/static/img/cordova_bot.png', true);
xhr.responseType = 'blob';
xhr.onload = function() {
if (this.status == 200) {
var blob = new Blob([this.response], { type: 'image/png' });
saveFile(dirEntry, blob, "downloadedImage.png");
}
};
xhr.send();
}
```
{% hint style="info" %}
For Cordova 5 security, the preceding code requires that you add the domain name, [`http://cordova.apache.org`](http://cordova.apache.org), to the **Content-Security-Policy** element in `index.html`.
{% endhint %}
After getting the file, copy the contents to a new file. The current DirectoryEntry object is already associated with the app cache.
```javascript
function saveFile(dirEntry, fileData, fileName) {
dirEntry.getFile(fileName, { create: true, exclusive: false }, function (fileEntry) {
writeFile(fileEntry, fileData);
}, onErrorCreateFile);
}
```
In writeFile, you pass in the Blob object as the dataObj and you will save that in the new file.
```javascript
function writeFile(fileEntry, dataObj, isAppend) {
// Create a FileWriter object for our FileEntry (log.txt).
fileEntry.createWriter(function (fileWriter) {
fileWriter.onwriteend = function() {
console.log("Successful file write...");
if (dataObj.type == "image/png") {
readBinaryFile(fileEntry);
}
else {
readFile(fileEntry);
}
};
fileWriter.onerror = function(e) {
console.log("Failed file write: " + e.toString());
};
fileWriter.write(dataObj);
});
}
```
After writing to the file, read it and display it. You saved the image as binary data, so you can read it using `FileReader.readAsArrayBuffer`.
```javascript
function readBinaryFile(fileEntry) {
fileEntry.file(function (file) {
var reader = new FileReader();
reader.onloadend = function() {
console.log("Successful file write: " + this.result);
displayFileData(fileEntry.fullPath + ": " + this.result);
var blob = new Blob([new Uint8Array(this.result)], { type: "image/png" });
displayImage(blob);
};
reader.readAsArrayBuffer(file);
}, onErrorReadFile);
}
```
After reading the data, you can display the image using code like this. Use `window.URL.createObjectURL` to get a DOM string for the Blob image.
```javascript
function displayImage(blob) {
// Displays image if result is a valid DOM string for an image.
var elem = document.getElementById('imageFile');
// Note: Use window.URL.revokeObjectURL when finished with image.
elem.src = window.URL.createObjectURL(blob);
}
```
### Display an image file
To display an image using a FileEntry, you can call the `toURL` method.
```javascript
function displayImageByFileURL(fileEntry) {
var elem = document.getElementById('imageFile');
elem.src = fileEntry.toURL();
}
```
If you are using some platform-specific URIs instead of a FileEntry and you want to display an image, you may need to include the main part of the URI in the Content-Security-Policy element in index.html. Here is an example.
```markup
```
### Create Directories
In the code here, you create directories in the root of the app storage location. You could use this code with any writable storage location (that is, any DirectoryEntry). Here, you write to the application cache (assuming that you used window\.TEMPORARY to get your FileSystem object) by passing fs.root into this function.
This code creates the /NewDirInRoot/images folder in the application cache. For platform-specific values, look at *File System Layouts*.
```javascript
function createDirectory(rootDirEntry) {
rootDirEntry.getDirectory('NewDirInRoot', { create: true }, function (dirEntry) {
dirEntry.getDirectory('images', { create: true }, function (subDirEntry) {
createFile(subDirEntry, "fileInNewSubDir.txt");
}, onErrorGetDir);
}, onErrorGetDir);
}
```
When creating subfolders, you need to create each folder separately as shown in the preceding code.