Native File System Typescript Typings – https://wicg.github.io/native-file-system/

index.ts

declare global {
    enum ChooseFileSystemEntriesType {
        'open-file',
        'save-file',
        'open-directory'
    }

    interface ChooseFileSystemEntriesOptionsAccepts {
        description?: string;
        mimeTypes?: string;
        extensions?: string;
    }

    interface ChooseFileSystemEntriesOptions {
        type?: ChooseFileSystemEntriesType;
        multiple?: boolean;
        accepts?: ChooseFileSystemEntriesOptionsAccepts[];
        excludeAcceptAllOption?: boolean;
    }

    interface FileSystemHandlePermissionDescriptor {
        writable?: boolean;
    }

    interface FileSystemCreateWriterOptions {
        keepExistingData?: boolean;
    }

    interface FileSystemGetFileOptions {
        create?: boolean;
    }

    interface FileSystemGetDirectoryOptions {
        create?: boolean;
    }

    interface FileSystemRemoveOptions {
        recursive?: boolean;
    }

    enum SystemDirectoryType {
        'sandbox'
    }

    interface GetSystemDirectoryOptions {
        type: SystemDirectoryType;
    }

    interface FileSystemWriter {
        write(position: number, data: BufferSource | Blob | string): Promise<void>;
        truncate(size: number): Promise<void>;
        close(): Promise<void>;
    }

    interface FileSystemWriterConstructor {
        new(): FileSystemWriter;
    }

    interface FileSystemHandle {
        isFile: Readonly<boolean>;
        isDirectory: Readonly<boolean>;
        name: Readonly<string>;
        queryPermission(descriptor?: FileSystemHandlePermissionDescriptor): Promise<PermissionState>;
        requestPermission(descriptor?: FileSystemHandlePermissionDescriptor): Promise<PermissionState>;
    }

    interface FileSystemHandleConstructor {
        new(): FileSystemHandle;
    }

    interface FileSystemFileHandle extends FileSystemHandle {
        getFile(): Promise<File>;
        createWriter(options?: FileSystemCreateWriterOptions): Promise<FileSystemWriter>;
    }

    interface FileSystemFileHandleConstructor {
        new(): FileSystemFileHandle;
    }

    interface FileSystemDirectoryHandle extends FileSystemHandle {
        getFile(name: string, options?: FileSystemGetFileOptions): Promise<FileSystemFileHandle>;
        getDirectory(name: string, options?: FileSystemGetDirectoryOptions): Promise<FileSystemDirectoryHandle>;
        getEntries(): AsyncIterable<FileSystemFileHandle | FileSystemDirectoryHandle>;
        removeEntry(name: string, options?: FileSystemRemoveOptions): Promise<void>;
    }

    interface FileSystemDirectoryHandleConstructor {
        new(): FileSystemDirectoryHandle;
        getSystemDirectory(options: GetSystemDirectoryOptions): Promise<FileSystemDirectoryHandle>;
    }

    interface Window {
        chooseFileSystemEntries(options?: ChooseFileSystemEntriesOptions): Promise<FileSystemHandle | FileSystemHandle[]>;
        FileSystemHandle: FileSystemHandleConstructor;
        FileSystemFileHandle: FileSystemFileHandleConstructor;
        FileSystemDirectoryHandle: FileSystemDirectoryHandleConstructor;
        FileSystemWriter: FileSystemWriterConstructor;
    }
}