readFileAs*

Promise wrappers around FileReader.

Function	Resolves with	Use for
readFileAsArrayBuffer(blob)	ArrayBuffer	Binary processing
readFileAsUint8Array(blob)	Uint8Array	Feeding checkEncoding / arrayBufferToString
readFileAsText(blob, encoding?)	string	Text files; sniff the encoding first if it is unknown
readFileAsDataURL(blob)	string	Image previews

Example

import { readFileAsUint8Array, arrayBufferToString } from 'ranuts';

input.addEventListener('change', async (e) => {
  const bytes = await readFileAsUint8Array(e.target.files[0]);
  const text = arrayBufferToString(bytes); // encoding is sniffed, GBK/Big5 included
});

Notes

1. All three exits are wired — onload, onerror and onabort. Forgetting onabort is the classic way to leave a promise pending forever when the user cancels the picker.
2. Rejects with a clear error where FileReader does not exist (Node, some worker contexts).
3. Never new TextDecoder().decode() a file of unknown origin — that assumes UTF-8 and turns GBK/Big5 into mojibake. Use arrayBufferToString, which sniffs first.