Using`await` out of asynchronous function causes syntax error

Question

I’m trying to make a function that awaits the answer, but the console points out an error:

var cota = await getJSON();
           ^^^^^
SyntaxError: await is only valid in async function

My code is:

async function getJSON() {
    var options = {
        url: "https://economia.awesomeapi.com.br/json/all",
        method: 'GET'
    }

    await request(options, function(error, response, body) {
        if (!error && response.statusCode == 200) {
            console.log(body)
            return body
        };
    });
};

var cota = await getJSON();

Answer 1

First of all, it is worth saying that its function is incorrect. The result of request will never be returned by getJSON, since the return is inside the callback of function request, and not of the getJSON. In that case, how are you working with a callback, I think it’s more interesting to return a Promise directly:

function getJSON() {
  const options = {
    url: 'https://economia.awesomeapi.com.br/json/all',
    method: 'GET'
  };

  return new Promise((resolve, reject) => {
    request(options, function(error, response, body) {
      if (error) {
        reject(error);
      } else {
        resolve(body);
      }
    });
  });
}
const cota = getJSON()
  .then((body) => {
    console.log('Recebi o body:', body);
  })
  .catch((error) => {
    console.error('Algo deu errado:', error);
  });

Note that in the above example, async was not necessary as the operator await was not used at any time within the function getJSON.

If you want to use asynchronous function, you can use the API fetch - which is a native alternative to the library request. Learn more here. Thus:

async function getJSON() {
  const response = await fetch('https://economia.awesomeapi.com.br/json/all');
  const body = await response.json();

  return body();
}
const cota = getJSON()
  .then((body) => {
    console.log('Recebi o body:', body);
  })
  .catch((error) => {
    console.error('Algo deu errado:', error);
  });

Now, let’s go to error:

SyntaxError: await is only valid in async function

The operator await can only be used within functions marked as async, as the error message left - at least in my view - very clear.

Therefore, you cannot use the await out of asynchronous functions, which makes the following snippet of your code invalid:

var cota = await getJSON();
//         ↑↑↑↑↑
//       INVÁLIDO, como está FORA de uma função marcada com o `async`

So you have two options:

1. Use the then, since every asynchronous function returns a Promise. I did this example above. Or:
2. Use another asynchronous function. Something like this:

async function getJSON() {
  const response = await fetch('https://economia.awesomeapi.com.br/json/all');
  const body = await response.json();

  return body();
}

(async () => {
  try {
    const body = await getJSON();
    console.log('Recebi o body:', body);
  } catch (error) {
    console.error('Algo deu errado:', error);
  }
})();

In the above case, I used an asynchronous IIFE.