FileReaderSync.readAsDataURL()

The readAsDataURL() method of the FileReaderSync interface allows to read File or Blob objects in a synchronous way into an DOMString representing a data URL. This interface is only available in workers as it enables synchronous I/O that could potentially block.

Syntax

readAsDataURL(File);
readAsDataURL(Blob);

Parameters

blob

The DOM File or Blob to read.

Return value

An DOMString representing the input data as a data URL.

Exceptions

The following exceptions can be raised by this method:

NotFoundError

is raised when the resource represented by the DOM File or Blob cannot be found, e.g. because it has been erased.

SecurityError

is raised when one of the following problematic situation is detected:

  • the resource has been modified by a third party;
  • too many read are performed simultaneously;
  • the file pointed by the resource is unsafe for a use from the Web (like it is a system file).
NotReadableError

is raised when the resource cannot be read due to a permission problem, like a concurrent lock.

EncodingError

is raised when the resource is a data URL and exceed the limit length defined by each browser.

Specifications

Specification
File API
# readAsDataURLSync-section

Browser compatibility

BCD tables only load in the browser

See also