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FileSystemHandle: requestPermission() method

files/en-us/web/api/filesystemhandle/requestpermission/index.md

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{{securecontext_header}}{{APIRef("File System API")}}{{AvailableInWorkers}}{{SeeCompatTable}}

The requestPermission() method of the {{domxref("FileSystemHandle")}} interface requests read or readwrite permissions for the file handle.

Syntax

js-nolint
requestPermission(descriptor)

Parameters

  • descriptor {{optional_inline}}
    • : An object which specifies the permission mode to query for. Options are as follows:
      • 'mode' {{optional_inline}}
        • : Can be either 'read', 'write', or 'readwrite'.

Return value

A {{jsxref("Promise")}} that resolves with {{domxref('PermissionStatus.state')}} which is one of 'granted', 'denied' or 'prompt'. It may also reject with one of the exceptions below.

Exceptions

  • {{jsxref("TypeError")}}
    • : Thrown if no parameter is specified or the mode is not that of 'read', 'write', or 'readwrite'
  • SecurityError {{domxref("DOMException")}}
    • : Thrown in one of the following cases:
      • The method was called in a context that's not same-origin as the top-level context (i.e., a cross-origin iframe).
      • There was no transient user activation such as a button press. This includes when the handle is in a non-Window context which cannot consume user activation, such as a worker.

Security

Transient user activation is required. The user has to interact with the page or a UI element in order for this feature to work.

Examples

The following asynchronous function requests permissions if they have not been granted.

js
// fileHandle is a FileSystemFileHandle
// withWrite is a boolean set to true if write

async function verifyPermission(fileHandle, withWrite) {
  const opts = {};
  if (withWrite) {
    opts.mode = "readwrite";
  }

  // Check if we already have permission, if so, return true.
  if ((await fileHandle.queryPermission(opts)) === "granted") {
    return true;
  }

  // Request permission to the file, if the user grants permission, return true.
  if ((await fileHandle.requestPermission(opts)) === "granted") {
    return true;
  }

  // The user did not grant permission, return false.
  return false;
}

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also