Desugared generator & async generator functions (for..of & for await..of)

. Desugared generator & async generator functions

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async-generator-desugared.js

function asyncGenFn() {
  let num = 1;

  return {
    [Symbol.asyncIterator]() {
      return this;
    },
    async next() {
      return (num <= 3) ?
        { value: num++, done: false } :
        { value: undefined, done: true };
    }
  };
}

(async () => {
  const asyncGen = asyncGenFn();

  let result = await asyncGen.next();

  while (!result.done) {
    const num = result.value;
    console.log(num);
    result = await asyncGen.next();
  }
})();

async-generator.js

async function* asyncGenFn() {
  let num = 1;
  while (num <= 3) {
    yield num++;
  }
}

(async () => {
  const asyncGen = asyncGenFn();

  for await (const num of asyncGen) {
    console.log(num);
  }
})();

generator-desugared.js

function genFn() {
  let num = 1;

  return {
    [Symbol.iterator]() {
      return this;
    },
    next() {
      return (num <= 3) ?
        { value: num++, done: false } :
        { value: undefined, done: true };
    }
  };
}

{
  const gen = genFn();

  let result = gen.next();

  while (!result.done) {
    const num = result.value;
    console.log(num);
    result = gen.next();
  }
}

generator.js

function* genFn() {
  let num = 1;
  while (num <= 3) {
    yield num++;
  }
}

{
  const gen = genFn();

  for (const num of gen) {
    console.log(num);
  }
}