FileReaderSync: readAsText() method

{{APIRef("File API")}} {{AvailableInWorkers("worker_except_service")}}

The readAsText() method of the {{DOMxRef("FileReaderSync")}} interface allows to read {{DOMxRef("File")}} or {{DOMxRef("Blob")}} objects in a synchronous way into a string. This interface is only available in workers as it enables synchronous I/O that could potentially block.

Syntax

readAsText(blob)
readAsText(blob, encoding)

Parameters

• blob
  • : The {{DOMxRef("File")}} or {{DOMxRef("Blob")}} to read.
• encoding {{optional_inline}}
  • : The optional parameter specifies encoding to be used (e.g., iso-8859-1 or UTF-8). If not present, the method will apply a detection algorithm for it.

Return value

A string representing the input data.

Exceptions

The following exceptions can be raised by this method:

• NotFoundError {{domxref("DOMException")}}
  • : Thrown if the resource represented by the DOM {{DOMxRef("File")}} or {{DOMxRef("Blob")}} cannot be found, e.g., because it has been erased.
• SecurityError {{domxref("DOMException")}}
  • : Thrown if 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 {{domxref("DOMException")}}
  • : Thrown if the resource cannot be read due to a permission problem, like a concurrent lock.
• EncodingError {{domxref("DOMException")}}
  • : Thrown if the resource is a data URL and exceed the limit length defined by each browser.

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• File API
• {{DOMxRef("File")}}
• {{DOMxRef("FileReaderSync")}}
• {{DOMxRef("FileReader")}}
• {{ domxref("Blob") }}