FileReader: readyState property

The FileReader readyState property provides the current state of the reading operation a FileReader is in. A FileReader exists in one of the following states:

Value	State	Description
0	EMPTY	Reader has been created. None of the read methods called yet.
1	LOADING	A read method has been called.
2	DONE	The operation is complete.

EMPTY

The FileReader has been created, but no readAs method was called yet.

LOADING

A readAs method was invoked. A File or Blob is being read, and no error has occurred yet.

DONE

The read operation is complete. This could mean that: the entire File or Blob has been read into memory, a file read error occurred, or abort() was called and the read was cancelled.

const reader = new FileReader();
console.log("EMPTY", reader.readyState); // readyState will be 0

reader.readAsText(blob);
console.log("LOADING", reader.readyState); // readyState will be 1

reader.onloadend = () => {
  console.log("DONE", reader.readyState); // readyState will be 2
};