FileReaderSync: readAsDataURL() method
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.
Note: This feature is only available in Web Workers, except for Service Workers.
The readAsDataURL()
method of the FileReaderSync
interface allows to read File
or Blob
objects in a synchronous way into a string representing a data URL. This interface is only available in workers as it enables synchronous I/O that could potentially block.
Syntax
readAsDataURL(blob)
Parameters
Return value
A string representing the input data as a data URL.
Exceptions
The following exceptions can be raised by this method:
NotFoundError
DOMException
-
Thrown if the resource represented by the DOM
File
orBlob
cannot be found, e.g. because it has been erased. SecurityError
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
DOMException
-
Thrown if the resource cannot be read due to a permission problem, like a concurrent lock.
EncodingError
DOMException
-
Thrown if 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