FileReaderSync: readAsText() method
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
Note: This feature is only available in Web Workers, except for Service Workers.
The readAsText() method of the FileReaderSync interface allows to read File or 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
blobencodingOptional-
The optional parameter specifies encoding to be used (e.g.,
iso-8859-1orUTF-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:
NotFoundErrorDOMException-
Thrown if the resource represented by the DOM
FileorBlobcannot be found, e.g., because it has been erased. SecurityErrorDOMException-
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).
NotReadableErrorDOMException-
Thrown if the resource cannot be read due to a permission problem, like a concurrent lock.
EncodingErrorDOMException-
Thrown if the resource is a data URL and exceed the limit length defined by each browser.
Specifications
| Specification |
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| File API # readAsTextSync |
Browser compatibility
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Legend
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- Full support
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