Cordova File API Wrapper

fileStorage.coffee

window.fileStorage =
    save: (name, data) ->
        deferred = $.Deferred()

        fail = (error) =>
            deferred.reject(error)

        gotFileSystem = (fileSystem) =>
            fileSystem.root.getFile(name, { create: true, exclusive: false }, gotFileEntry, fail)

        gotFileEntry = (fileEntry) =>
            fileEntry.createWriter(gotFileWriter, fail)

        gotFileWriter = (writer) =>
            writer.onwrite = () =>
                deferred.resolve()

            writer.onerror = fail
            writer.write(data)

        window.requestFileSystem(window.LocalFileSystem.PERSISTENT, data.length || 0, gotFileSystem, fail)
        return deferred.promise()

    load: (name) ->
        deferred = $.Deferred()

        fail = (error) =>
            deferred.reject(error)

        gotFileSystem = (fileSystem) =>
            fileSystem.root.getFile(name, { create: false, exclusive: false }, gotFileEntry, fail)

        gotFileEntry = (fileEntry) =>
            fileEntry.file(gotFile, fail)

        gotFile = (file) =>
            reader = new FileReader()
            reader.onloadend = (evt) =>
                data = evt.target.result
                deferred.resolve(data)

            reader.readAsText(file)

        window.requestFileSystem(window.LocalFileSystem.PERSISTENT, 0, gotFileSystem, fail)
        return deferred.promise()

    delete: (name) =>
        deferred = $.Deferred()

        fail = (error) =>
            deferred.reject(error)

        gotFileSystem = (fileSystem) =>
            fileSystem.root.getFile(name, { create: false, exclusive: false }, gotFileEntry, fail)

        gotFileEntry = (fileEntry) =>
            fileEntry.remove()

        window.requestFileSystem(window.LocalFileSystem.PERSISTENT, 0, gotFileSystem, fail)
        return deferred.promise()

This code is discussed in a blog post: Using Deferreds with the Cordova File API

This saved my butt. I was banging my head against the wall for the past two weeks trying to get file writing / reading working in Cordova to no avail. This code sample did it for me. Also see my fork with a few simplifications & support for traversing directories!

Thank you both for the code!

I've updated it to use standard Promises now that they're well supported.

I also added JSDoc comments and returned the filename from the fileStorage.write method.