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Is it possible to convert FileEntry to standard JavaScript object File? I can't find anything meaningful in documentation https://developer.chrome.com/apps/fileSystem

Michał Jereczek
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2 Answers2

27

The FileEntry documentation does provide guidance here:

The FileSystemFileEntry interface of the File System API represents a file in a file system. It offers properties describing the file's attributes, as well as the file() method, which creates a File object that can be used to read the file.

Unfortunately file()method relies on callbacks rather Promises, but we can wrap that and make using the API (and reading the code) easier:

async function getFile(fileEntry) {
  try {
    return new Promise((resolve, reject) => fileEntry.file(resolve, reject));
  } catch (err) {
    console.log(err);
  }
}

// From inside an async method or JS module
let file = await getFile(fileEntry); // Wait until we have the file
xlm
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    Hi, I was curious why you used async and await when defining `getFile`. Would it not work the same if you got rid of them, and just returned the promise directly? – ack_inc Sep 27 '22 at 14:12
  • @ack_inc yes you're right, it doesn't add anything, thanks for picking that up. Edited per your comment. – xlm Sep 28 '22 at 01:25
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I found how to do this in google examples https://github.com/GoogleChrome/chrome-app-samples/blob/master/samples/filesystem-access/js/app.js

var jsFileObject;
fileEntry.file(function (file){ 
   jsFileObject = file 
});
Michał Jereczek
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    Don't forget the error callback! You will silently never get a callback in some (albeit) rare cases. The signature should be `entry.file(success,error)` – kzahel Jul 20 '17 at 22:19
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    Take note that this code is asynchronous: you can't immediately use `jsFileObject`. See xlm's [answer](https://stackoverflow.com/a/53113059/934239) for a Promise-based solution to that problem. – Xan Nov 02 '18 at 09:44