Nodejs convert string into UTF-8

Use the utf8 module from npm to encode/decode the string.

Installation:

npm install utf8

In a browser:

<script src="utf8.js"></script>

In Node.js:

const utf8 = require('utf8');

API:

Encode:

utf8.encode(string)

Encodes any given JavaScript string (string) as UTF-8, and returns the UTF-8-encoded version of the string. It throws an error if the input string contains a non-scalar value, i.e. a lone surrogate. (If you need to be able to encode non-scalar values as well, use WTF-8 instead.)

// U+00A9 COPYRIGHT SIGN; see http://codepoints.net/U+00A9
utf8.encode('\xA9');
// → '\xC2\xA9'
// U+10001 LINEAR B SYLLABLE B038 E; see http://codepoints.net/U+10001
utf8.encode('\uD800\uDC01');
// → '\xF0\x90\x80\x81'

Decode:

utf8.decode(byteString)

Decodes any given UTF-8-encoded string (byteString) as UTF-8, and returns the UTF-8-decoded version of the string. It throws an error when malformed UTF-8 is detected. (If you need to be able to decode encoded non-scalar values as well, use WTF-8 instead.)

utf8.decode('\xC2\xA9');
// → '\xA9'

utf8.decode('\xF0\x90\x80\x81');
// → '\uD800\uDC01'
// → U+10001 LINEAR B SYLLABLE B038 E

Resources

I'd recommend using the Buffer object:

var someEncodedString = Buffer.from('someString', 'utf-8').toString();

This avoids any unnecessary dependencies that other answers require, since Buffer is included with node.js, and is already defined in the global scope.