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Async (mark function as async??)

JavaScript

async.js Raw #

// https://stackoverflow.com/questions/44106907/when-to-mark-function-as-async

async function fnUsingAsync() {
    // Synchronously throw half of the time
    if (Math.random() < .5)
        throw new Error('synchronous error')

    // Return fulfilled/rejected promises half of the time
    return Math.random() < .5 ?
        Promise.resolve('success') :
        Promise.reject(new Error('asynchronous error');
}

function fnNotUsingAsync(x) {
    // Use the exact same body here than function above
}



// when using the async keyword, the function always returns a promise
// which can be fulfilled or rejected.
// No need for try-catch!
fnUsingAsync()
    .then(result => /* result === 'success' */)
    .catch(error => /* catch both synchronous and asynchronous error */);

// Otherwise, you will need to use a try-catch statement, because
// the exception won't be converted to a rejected promise.
try {
    fnNotUsingAsync()
      .then(result => /* result === 'success' */)
      .catch(error => /* catch asynchronous error only */)
}
catch (error) {
    /* catch synchronous error only */
}