This is a port of the work done by Chris Veness over the past ten years in relation to encoding and decoding Utf-8 data in a JavaScript environment. I didn't write the core of this, merely modified it to work with Node's package structure and be published on npm, where people can by and large get used to it and stop being confused about this issue. ;P
npm install utf8
var utf8 = require('utf8');
var c = utf8.encode("私は")
utf8.decode(c);