バイナリ職人

binary.md

hex string -> buffer

const hexString = '00AA55FF';
const buffer = Buffer.from(hexString, 'hex'); // <Buffer 00 aa 55 ff>

const firstByte = buffer.slice(1, 3) // <Buffer aa 55>

buffer -> hex string

const buffer = Buffer.from([0x00, 0xaa, 0x55, 0xff]); // <Buffer 00 aa 55 ff>
const hexString = buffer.toString('hex'); // '00AA55FF'

little endian

const buffer = Buffer.from([0x00, 0xaa, 0x55, 0xff]); // <Buffer 00 aa 55 ff>
buffer.readUIntLE(0, 2); // <Buffer aa 00>

String -> Ascii code

const str = 'abcABC';
Buffer.from(str).toString('hex'); // -> '616263414243'
str.split('').map(c => c.charCodeAt(0).toString(16)).join('') // -> '616263414243'