Science Knowings: HTML Course For Social Media

HTML5 FileSystem API

Moving from HTML5 Streams API to HTML5 FileSystem API

In the previous session, we covered the HTML5 Streams API and its capabilities. Today, we'll shift our focus to a new topic: the HTML5 FileSystem API.

What is the File System API?

The HTML5 File System API provides a way for web applications to interact with the file system of the user's computer. This allows web apps to read, write, and delete files and create and manage directories.

Why Use the File System API?

The File System API has several advantages over traditional file handling techniques:

  • Cross-platform compatibility: Works on all major browsers.
  • Asynchronous operation: Doesn't block the main thread, allowing for responsive web applications.
  • Security: Provides a secure way to access local files, preventing unauthorized access.

Permissions in the File System API

To use the File System API, web applications must request permission from the user to access the file system. This permission can be granted or denied by the user.

Opening and Reading Files

To open and read a file, you can use the window.resolveLocalFileSystemURL method and the FileReader object.

window.resolveLocalFileSystemURL(filePath, function(fileEntry) { 
  fileEntry.file(function(file) { 
    const reader = new FileReader(); 
    reader.onloadend = function() { 
      console.log(reader.result); 
    }; 
    reader.readAsText(file); 
  }); 
});

Writing to Files

To write to a file, you can use the FileWriter object. First, create a new file or open an existing one, then use the write method to write data to the file.

fileEntry.createWriter(function(fileWriter) { 
  fileWriter.onwriteend = function() { 
    console.log('Write completed.'); 
  }; 
  fileWriter.write(new Blob(['Hello, world!'])); 
});

Creating and Deleting Directories

To create a new directory, use the getDirectory method with the create option set to true. To delete a directory, use the removeRecursively method.

fileSystem.root.getDirectory('myDirectory', {create: true}, function(dirEntry) { 
  console.log('Directory created.'); 
});

Navigating the File System

You can use the DirectoryEntry object to navigate the file system and get information about files and directories.

dirEntry.getDirectory('subdirectory', function(subDirEntry) { 
  subDirEntry.getFile('myfile.txt', function(fileEntry) { 
    console.log('File found.'); 
  }); 
});

File System API Methods

MethodDescription
resolveLocalFileSystemURLResolves a local file system URL to a DirectoryEntry or FileEntry.
getDirectoryGets a directory.
getFileGets a file.
createWriterCreates a FileWriter object.
removeRecursivelyDeletes a directory and all of its contents.

File System API Events

EventDescription
onloadendFired when a file operation completes.
onprogressFired when a file operation is in progress.
onerrorFired when an error occurs during a file operation.

Cross-Origin Issues

The File System API can be affected by cross-origin issues if the web application is trying to access files from a different domain than the one it is hosted on.

Next Up: HTML5 Timing and Performance API

In the next session, we'll explore the HTML5 Timing and Performance API, which provides tools for measuring and improving the performance of web applications.