ECMAScript 2017 `async` in macOS Sierra JavaScriptCore

es2016-jxa.js

#!/usr/bin/env osascript -l JavaScript

// macOS Sierra uses a JavaScriptCore analagous to that in Safari 10.1. This supports all of
// ECMAScript 2015 (“ES6”), and even much of ECMAScript 2016! For instance, try `async` functions:
async function hello(){
   return "Hello, world!"
}

function run(argv) {
   var p = hello();

   if (!(p instanceof Promise)) throw "No ES2016 support."

   p.then(result => console.log(result + " (async!)") )
}

this. is. amazing.