For the latest updates on HTML5 features, check out this informative article at http://www.html5rocks.com/en/tutorials/file/dndfiles/. This resource provides a detailed explanation of local file access using JavaScript. Here's a summary from the article:

The HTML5 specification offers various interfaces for accessing files from a 'local' filesystem:

1. File - represents an individual file and includes read-only information such as name, size, MIME type, and a file handle reference.
2. FileList - a list-like collection of File objects, commonly used with elements like

   <input type="file" multiple>

   or when dragging files from a desktop directory.
3. Blob - enables slicing a file into byte ranges for easier manipulation.

Be sure to read Paul D. Waite's insightful comment below this post.

Exploring the capabilities of the FileSystem, File, and FileWriter APIs allows users to interact with files within a browser tab/window and on their local machines.

Several key points about these APIs are worth noting:

• The implementation of these APIs is currently limited to Chromium-based browsers such as Chrome and Opera
• They were removed from the W3C standards track in 2014, making them proprietary technologies
• There is a possibility that implementing browsers may phase out support for these APIs in the future
• A secure sandbox is used to store files created through these APIs
• A virtual file system is employed to manage files, offering a unique way to organize data within the browser environment

Examples demonstrate how these APIs can be utilized:

BakedGoods*

For writing a file:

bakedGoods.set({
    data: [{key: "testFile", value: "Hello world!", dataFormat: "text/plain"}],
    storageTypes: ["fileSystem"],
    options: {fileSystem:{storageType: Window.PERSISTENT}},
    complete: function(byStorageTypeStoredItemRangeDataObj, byStorageTypeErrorObj){}
});

For reading a file:

bakedGoods.get({
        data: ["testFile"],
        storageTypes: ["fileSystem"],
        options: {fileSystem:{storageType: Window.PERSISTENT}},
        complete: function(resultDataObj, byStorageTypeErrorObj){}
});

In addition to using frameworks like BakedGoods, direct use of the raw File, FileWriter, and FileSystem APIs offer flexibility:

Writing a file:

// Code snippet for saving a file
function onQuotaRequestSuccess(grantedQuota)
{
    // Callback function for handling directory entry
    function saveFile(directoryEntry)
    {
        // Callback function for creating a new file writer
        function createFileWriter(fileEntry)
        {
            // Function for writing content to file
            function write(fileWriter)
            {
                var dataBlob = new Blob(["Hello world!"], {type: "text/plain"});
                fileWriter.write(dataBlob);              
            }

            fileEntry.createWriter(write);
        }

        directoryEntry.getFile(
            "testFile", 
            {create: true, exclusive: true},
            createFileWriter
        );
    }

    var desiredQuota = 1024 * 1024 * 1024;
    var quotaManagementObj = navigator.webkitPersistentStorage;
    quotaManagementObj.requestQuota(desiredQuota, onQuotaRequestSuccess);
}

// Initiate request for storage quota
var desiredQuota = 1024 * 1024 * 1024;
var quotaManagementObj = navigator.webkitPersistentStorage;
quotaManagementObj.requestQuota(desiredQuota, onQuotaRequestSuccess);

Reading a file:

// Code snippet for retrieving a file
function onQuotaRequestSuccess(grantedQuota)
{
    // Callback function for accessing file from directory
    function getFile(directoryEntry)
    {
        // Callback function for reading file content
        function readFile(fileEntry)
        {
            // Function for reading file using FileReader API
            function read(file)
            {
                var fileReader = new FileReader();

                fileReader.onload = function(){var fileData = fileReader.result};
                fileReader.readAsText(file);             
            }

            fileEntry.file(read);
        }

        directoryEntry.getFile(
            "testFile", 
            {create: false},
            readFile
        );
    }

    var desiredQuota = 1024 * 1024 * 1024;
    var quotaManagementObj = navigator.webkitPersistentStorage;
    quotaManagementObj.requestQuota(desiredQuota, onQuotaRequestSuccess);
}

// Initiating storage quota request
var desiredQuota = 1024 * 1024 * 1024;
var quotaManagementObj = navigator.webkitPersistentStorage;
quotaManagementObj.requestQuota(desiredQuota, onQuotaRequestSuccess);

Though no longer part of standardization efforts, these APIs remain relevant due to potential market developments:

• Rising interest could lead other browsers to adopt these technologies
• Chromium's widespread usage supports continued access to these features
• Google, a major player in the development of Chromium, has not announced plans to retire these APIs

Deciding if these APIs suit your needs is ultimately up to you.

*BakedGoods is maintained by yours truly :)

UPDATE As of Firefox 17, this feature has been removed. (View https://bugzilla.mozilla.org/show_bug.cgi?id=546848 for more information).

In Firefox, JavaScript files can no longer perform the following actions:

netscape.security.PrivilegeManager.enablePrivilege("UniversalBrowserRead");
netscape.security.PrivilegeManager.enablePrivilege("UniversalBrowserWrite");

Browser users will now be prompted to grant access themselves. Please note that permission must be granted each time the browser is opened.

If a different user is using the browser, they will need to give permission themselves.

With NW.js, developers can harness the power of Javascript to build desktop applications free from typical browser security restrictions. This means being able to perform tasks like running executables or manipulating files without limitation. Additionally, access to hardware resources such as CPU usage and RAM is made possible.

The flexibility extends to creating desktop applications for Windows, Linux, or Mac platforms that can be used without the need for installation.

For those working on Windows systems, the Windows Script Host provides a valuable JScript API for accessing file systems and other local resources. While integrating WSH scripts into a local web application may not be as seamless as desired, it can still offer significant functionality.

When dealing with an input field of the following nature:

<input type="file" id="file" name="file" onchange="add(event)"/>

It is possible to access the file content in BLOB format using the function below:

function add(event){
  var userFile = document.getElementById('file');
  userFile.src = URL.createObjectURL(event.target.files[0]);
  var data = userFile.src;
}

FSO.js is a powerful tool that harnesses the capabilities of the new HTML5 FileSystem API. This API, currently being standardized by the W3C, offers an extremely easy solution for tasks such as reading from, writing to, or navigating through a local sandboxed file system. With its asynchronous design, file I/O operations can be seamlessly executed without causing any disruptions to the user experience. :)

If you require full access to the complete file system on the client side, including read/write capabilities, monitoring folders for changes, launching applications, encrypting or signing documents, and more, consider utilizing JSFS.

JSFS allows for secure and unrestricted access from your webpage to computer resources on the client without the need for browser plugins like ActiveX or Java Applets. However, a software component must be installed as well.

Prior experience with Java and Java EE development (Servlets) is recommended in order to effectively utilize JSFS.

You can find JSFS at this link: https://github.com/jsfsproject/jsfs. It is available for free and licensed under GPL.

Introducing a revolutionary product known as "localFS," designed for reading and writing the entire file-system on the client's computer.

All it takes is installing a small Windows app and including a tiny .js file in your web page.

For added security, access to the file-system can be restricted to a single folder and protected with a secret key.

Learn more about localFS here!

In order for JavaScript code to access any necessary file, users must explicitly allow it. Most popular browsers do not grant permission for JavaScript to access files directly.

The solution revolves around the concept that JavaScript cannot access a file using its local URL. However, it can utilize the file through its DataURL. Therefore, when a user selects and opens a file, JavaScript should retrieve the "DataURL" from the HTML instead of the "URL".

To achieve this, the DataURL is converted into a file by utilizing the readAsDataURL function and FileReader object. For more details and a comprehensive guide, refer to:

https://developer.mozilla.org/en-US/docs/Web/API/FileReader?redirectlocale=en-US&redirectslug=DOM%2FFileReader

It's interesting to note that not many people are aware of this fact. Most programming languages cannot directly manipulate the filesystem themselves; they rely on operating system interrupts to do so. Even JavaScript, when running in a browser, can only work with browser "interrupts" and typically does not have filesystem access. However, if you want to interact with the filesystem using JavaScript, Node.js is a great option as it allows direct communication with the OS.

Exploring the new possibilities of Javascript's file system API is crucial for web developers.

window.showSaveFilePicker function enables users to save files locally with read/write access.

window.showOpenFilePicker function allows us to interact with existing files on a user's device.

window.showDirectoryPicker function provides access to directories for read/write operations.

For a detailed tutorial, visit https://example.com/article/javascript-file-system-api