async-gen-race.js

let caps = [];
async function* SpeedRacer() {
  yield new Promise(function(resolve, reject) {
    caps.push({ resolve, reject });
  });
  
  yield new Promise(function(resolve, reject) {
    caps.push({ resolve, reject });
  });
}

let it = SpeedRacer();

it.next().then(({ value, done }) => {
  console.log(`Yield #1 is done!: { value: ${value}, done: ${done} }`);
});

it.next().then(({ value, done }) => {
  console.log(`Yield #2 is done!: { value: ${value}, done: ${done} }`);
});

caps[1].resolve("Number2");
caps[0].resolve("Number1");

// If resolved in this order, should log:
//   `Yield #2 is done!: { value: Number2, done: false }`
//   `Yield #1 is done!: { value: Number1, done: false }`