NodeJS compartible Buffer implemenattion. See original Buffer doumentation

Two additional methods are adedd for converting between any codepage

Buffer.prototype.cpSlice:

 let arr = fs.readFileSync(path.join(__dirname, 'win1251Encoded.XML'), {encoding: 'binary'})
 let buffer = Buffer.from(arr)
 let strData = buffer.cpSlice(0, buffer.length, 1251)

Buffer.cpFrom(string, encobingNum): Buffer:

const buffer = Buffer.cpFrom('here text in cyrilic', 1251) // result is Win-1251 encoded string representation