Creating a temporary file

Elm:
Creating a temporary file

How to:

Elm runs in browsers, so it doesn’t have direct filesystem access. Therefore, you can’t create traditional temporary files. But, if you need a similar feature, we use Elm ports to interact with JavaScript, which can handle temporary file creation.

port module Main exposing (..)

-- Define a port for creating a temporary file in JavaScript
port createTempFile : String -> Cmd msg

-- Send data to JavaScript to create a temporary file
saveDataTemporarily : String -> Cmd msg
saveDataTemporarily data =
    createTempFile data

For the JavaScript part, using the File API:

app.ports.createTempFile.subscribe(function(data) {
    var blob = new Blob([data], {type: 'text/plain'});
    var url = URL.createObjectURL(blob);

    // Here you can use the URL to download the blob or pass it to other parts of your app
    console.log(url);  // It logs the temporary file URL
});

Sample output in JavaScript console:

blob:null/2135a9b7-1aad-4e7a-8bce-19c4f3f6d7ff

Deep Dive

Elm is designed to be safe and reliable, so direct file system access isn’t in the cards. Instead, Elm uses ports to communicate with JavaScript, allowing for operations like creating temporary files. Historically, we handle file-based tasks in the browser through JavaScript APIs, using Elm for type-safe, high-level logic.

Alternatives like WebAssembly may allow more direct filesystem interactions in the future, but for now, interop with JavaScript is the standard practice.

Implementation-wise, creating temporary files in the browser context does not mean an actual file on the filesystem, but rather an in-memory representation (blob) that you can work with and save as needed.

Elm:Creating a temporary file

How to:

Deep Dive

See Also

Elm:
Creating a temporary file