File System API

async function getFile() {
  //         
  const [fileHandle] = await window.showOpenFilePicker();
  const file = await fileHandle.getFile();
  return file;
}

const pickerOpts = {
  types: [
    {
      description: "Images",
      accept: {
        "image/*": [".png", ".gif", ".jpeg", ".jpg"],
      },
    },
  ],
  excludeAcceptAllOption: true,
  multiple: false,
};

async function getTheFile() {
  //         
  const [fileHandle] = await window.showOpenFilePicker(pickerOpts);

  //   
  const fileData = await fileHandle.getFile();
}

const dirName = "directoryToGetName";

// 'currentDirHandle'      
const subDir = currentDirHandle.getDirectoryHandle(dirName, { create: true });

async function returnPathDirectories(directoryHandle) {
  //      
  const [handle] = await self.showOpenFilePicker();
  if (!handle) {
    //       
    return;
  }

  //         
  const relativePaths = await directoryHandle.resolve(handle);

  if (relativePaths === null) {
    //    
  } else {
    // relativePaths      

    for (const name of relativePaths) {
      //   
      console.log(name);
    }
  }
}

async function saveFile() {
  //   
  const newHandle = await window.showSaveFilePicker();

  // Blob  FileSystemWritableFileStream 
  const writableStream = await newHandle.createWritable();

  //  
  await writableStream.write(imgBlob);

  //       
  await writableStream.close();
}

//   
writableStream.write(data);

//       
writableStream.write({ type: "write", position, data });

//      
writableStream.write({ type: "seek", position });

//  size    
writableStream.write({ type: "truncate", size });

onmessage = async (e) => {
  //     
  const message = e.data;

  // OPFS     
  const root = await navigator.storage.getDirectory();
  const draftHandle = await root.getFileHandle("draft.txt", { create: true });
  //    
  const accessHandle = await draftHandle.createSyncAccessHandle();

  //   
  const fileSize = accessHandle.getSize();
  //    
  const buffer = new DataView(new ArrayBuffer(fileSize));
  const readBuffer = accessHandle.read(buffer, { at: 0 });

  //    
  const encoder = new TextEncoder();
  const encodedMessage = encoder.encode(message);
  const writeBuffer = accessHandle.write(encodedMessage, { at: readBuffer });

  //  
  accessHandle.flush();

  //     FileSystemSyncAccessHandle 
  accessHandle.close();
};