harmony.sh

╭─sent1nel@syndicate  ~ ‹2.1.1›
╰─$ cat greeter.js
class Greeter {
  constructor(name) {
    this.name = name;
  }

  greeting() {
    return `Hey, ${this.name}!`;
  }

  greet() {
    console.log(this.greeting());
  }
}

var greeter = new Greeter('sent1nel');
greeter.greet();
╭─sent1nel@syndicate  ~ ‹2.1.1›
╰─$ iojs --harmony_modules --harmony_classes --use_strict greeter.js
Hey, sent1nel!