This API allows interaction with files on a user's local device, or on a user-accessible network file system. Core functionality of this API includes reading files, writing or saving files, and access to directory structure.
Most of the interaction with files and directories is accomplished through handles. A parent
The handles represent a file or directory on the user's system. You can first gain access to them by showing the user a file or directory picker using methods such as
1. Once these are called, the file picker presents itself and the user selects either a file or directory. Once this happens successfully, a handle is returned.
You can also gain access to file handles via:
Each handle provides its own functionality and there are a few differences depending on which one you are using (see the section for specific details). You then can access file data, or information (including children) of the directory selected. This API opens up potential functionality the web has been lacking. Still, security has been of utmost concern when designing the API, and access to file/directory data is disallowed unless the user specifically permits it.
Note: The different exceptions that can be thrown when using the features of this API are listed on relevant pages as defined in the spec. However, the situation is made more complex by the interaction of the API and the underlying operating system. A proposal has been made to list the error mappings in the spec, which includes useful related information.
Note: Objects based on
The is a storage endpoint private to the origin of the page, providing optional access to a special kind of file that is highly optimized for performance, for example, by offering in-place and exclusive write access to a file's content.
Storing data in the OPFS is similar to storing data in any other browser-provided storage mechanism that's private to the origin of the page (for example the IndexedDB API). This means that files in the OPFS differ from files selected using a picker in the following ways:
Files can be manipulated inside the OPFS via a three-step process:
While browsers typically implement this by persisting the contents of the OPFS to disk somewhere, it is not intended that the contents be easily user-accessible. While the browser might make it seem that there are files, they might be stored in a database or any other data structure. You cannot expect to find the created files matched one-to-one somewhere on the hard disk.
Note: Writes performed using
2 are in-place, meaning that changes are written to the actual underlying file at the same time as they are written to the writer. This is not the case with other writing mechanisms available in this API (e.g.
3), where changes are not committed to disk until the writing stream is closed.
There is also "save" functionality:
Provides a handle to a file system entry.
provides a handle to a file system directory.
Provides a synchronous handle to a file system entry, which operates in-place on a single file on disk. The synchronous nature of the file reads and writes allows for higher performance for critical methods in contexts where asynchronous operations come with high overhead, e.g., WebAssembly. This class is only accessible inside dedicated Web Workers for files within the .
0 object with additional convenience methods, which operates on a single file on disk.
The below code allows the user to choose a file from the file picker and then tests to see whether the handle returned is a file or directory
The following asynchronous function presents a file picker and once a file is chosen, uses the
1 method to retrieve the contents.
The following example returns a directory handle with the specified name. If the directory does not exist, it is created.
The following asynchronous function uses
2 to find the path to a chosen file, relative to a specified directory handle.
The following asynchronous function opens the save file picker, which returns a
A user defined
5 is then written to the stream which is subsequently closed.
The following show different examples of options that can be passed into the
This example synchronously reads and writes a file to the .
The following asynchronous event handler function is contained inside a Web Worker. On receiving a message from the main thread it:
Note: In earlier versions of the spec,
1 were wrongly specified as asynchronous methods. This has now been amended, but some browsers still support the asynchronous versions.
you can also use window. showDirectoryPicker() to ask for a specific folder and ask for write permission to that folder... then you can write data to wherever you want without prompting the user further. this new picker should have an option for hinting where it should save a file.
How do I save a file to a specific location?
Type the combination Shift+Ctrl+s, typing all three keys simultaneously. Both methods will launch the File Save dialog to allow the user to name the file, select a folder (also called a directory) for the file and choose a file format type.
How do I save a file to a specific folder in node JS?
You then use the writeFile() function of the fs module to create a file and write data to it. The first argument is the file path. As you provided just the file name, Node. js will create the file in the same directory that you're executing the code in.
Step 1 − Create HTML <a> element..
Step 2 − Get content to add to the text file..
Step 3 − Create a Blob object of the content..
Step 4 − In the href attribute of the <a> tag, add the blog object URL..
Step 5 − Add the default file name as a value of the 'download' attribute of <a> tag..