Downloading files with a Firefox addon

Question

I'm new to Firefox addon development, and it's going well so far, but I'm stuck on how to, essentially, download a file from the Web, given a URI, and save it to disk. Mozilla's MDN documentation has information on how to upload files, but the downloading files section is empty and yet to be written. Sadly, I haven't found any documentation which describes how to do this.

Does anyone know of relevant documentation on how to do this?

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The old Facebook Photo Album Downloader addon uses this function call in its overlay JavaScript:

saveURL(images[i].replace(/\/s/g, "/n"), null, null, false, true, null);

Obviously, the first argument is the URI to request. The saveURL function isn't defined anywhere, so I assume it's an extension API function. I have tried it in my new addon, and it does work. I would, however, like to know what the other arguments mean.

Answer 1

The standard way to do this is with nsIWebBrowserPersist:

var persist =
  Cc["@mozilla.org/embedding/browser/nsWebBrowserPersist;1"].
  createInstance(Ci.nsIWebBrowserPersist);
persist.saveURI(serverURI, null, null, null, "", targetFile);

See https://developer.mozilla.org/en/Code_snippets/Downloading_Files for more info.

Answer 2

There actually is some MDN documentation on this: https://developer.mozilla.org/en/Code_snippets/Downloading_Files.