The Bun.file() function accepts a path and returns a BunFile instance. The BunFile class extends Blob and allows you to lazily read the file in a variety of formats.
To read the file into a Uint8Array instance, retrieve the contents of the BunFile as an ArrayBuffer with .arrayBuffer(), then pass it into the Uint8Array constructor.
const path = "/path/to/package.json";
const file = Bun.file(path);
const arrBuffer = await file.arrayBuffer();
const byteArray = new Uint8Array(arrBuffer);
byteArray[0]; // first byteArray
byteArray.length; // length of byteArray
Refer to API > Binary data > Typed arrays for more information on working with Uint8Array and other binary data formats in Bun.