Why Do Async/Await Functions Always Return Promises?

Async/Await: Unveiling the Mystery of Promises

When embarking on the realm of async/await functionality, one may encounter an intriguing conundrum. It appears that async functions always return Promise objects, leading to confusion when attempting direct console logging.

Let's delve deeper into this phenomenon and unravel its intricacies. Every async function conforms to the Promise paradigm, returning a Promise object that encapsulates the result of the operation. The await statement serves as a means of pausing the execution of the function until the Promise either resolves or rejects.

While one might assume that await automatically unwraps the Promise, that is not the case. Using await merely causes the function to wait and subsequently return a Promise that resolves immediately. However, the Promise needs to be explicitly unwrapped using await or .then() to access the actual result.

To illustrate, consider the following code snippet that simulates an asynchronous request:

const getJSON = async () => {
  const request = () => new Promise((resolve, reject) => (
    setTimeout(() => resolve({ foo: 'bar'}), 2000)
  ));

  const json = await request();
  return json;
};

If one attempts to console log the result directly, the output will be a Promise:

console.log(getJSON()); // returns Promise

However, using .then() to unwrap the Promise reveals the expected JSON object:

getJSON().then(json => console.log(json)); // prints { foo: 'bar' }

In conclusion, async functions always return Promises, and await merely suspends execution until resolution. To obtain the result, explicit unwrapping using await or .then() is necessary. This mechanism ensures the integrity of the Promise model and prevents the unpredictable behavior that could arise if direct access to Promise results were permitted.

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