FileSystemDirectoryEntry

// Taking care of the browser-specific prefixes.
window.requestFileSystem =
  window.requestFileSystem || window.webkitRequestFileSystem;
window.directoryEntry = window.directoryEntry || window.webkitDirectoryEntry;

// …

function onFs(fs) {
  fs.root.getDirectory(
    "Documents",
    { create: true },
    (directoryEntry) => {
      // directoryEntry.isFile === false
      // directoryEntry.isDirectory === true
      // directoryEntry.name === 'Documents'
      // directoryEntry.fullPath === '/Documents'
    },
    onError,
  );
}

// Opening a file system with temporary storage
window.requestFileSystem(TEMPORARY, 1024 * 1024 /* 1MB */, onFs, onError);