List of encodings that Node.js supports

The list of encodings that node supports natively is rather short:

• ascii
• base64
• base64url (Node v14+)
• hex
• ucs2/ucs-2/utf16le/utf-16le
• utf8/utf-8
• binary/latin1 (ISO8859-1, latin1 only in node 6.4.0+)

If you are using an older version than 6.4.0, or don't want to deal with non-Unicode encodings, you can recode the string:

Use iconv-lite to recode files:

var iconvlite = require('iconv-lite');
var fs = require('fs');

function readFileSync_encoding(filename, encoding) {
    var content = fs.readFileSync(filename);
    return iconvlite.decode(content, encoding);
}

Alternatively, use iconv:

var Iconv = require('iconv').Iconv;
var fs = require('fs');

function readFileSync_encoding(filename, encoding) {
    var content = fs.readFileSync(filename);
    var iconv = new Iconv(encoding, 'UTF-8');
    var buffer = iconv.convert(content);
    return buffer.toString('utf8');
}

The encodings are spelled out in the buffer documentation.

Buffers and character encodings:

Character Encodings

• utf8: Multi-byte encoded Unicode characters. Many web pages and other document formats use UTF-8. This is the default character encoding.
• utf16le: Multi-byte encoded Unicode characters. Unlike utf8, each character in the string will be encoded using either 2 or 4 bytes.
• latin1: Latin-1 stands for ISO-8859-1. This character encoding only supports the Unicode characters from U+0000 to U+00FF.

Binary-to-Text Encodings

• base64: Base64 encoding. When creating a Buffer from a string, this encoding will also correctly accept "URL and Filename Safe Alphabet" as specified in RFC 4648, Section 5.
• base64url (Node v14+): base64url encoding as specified in RFC 4648, Section 5. When creating a Buffer from a string, this encoding will also correctly accept regular base64-encoded strings. When encoding a Buffer to a string, this encoding will omit padding.
• hex: Encode each byte as two hexadecimal characters.

Legacy Character Encodings

• ascii: For 7-bit ASCII data only. Generally, there should be no reason to use this encoding, as 'utf8' (or, if the data is known to always be ASCII-only, 'latin1') will be a better choice when encoding or decoding ASCII-only text.
• binary: Alias for 'latin1'.
• ucs2: Alias of 'utf16le'.