How to handle an error in async await in JavaScript

Last updated on Sep 24, 2020 by Suraj Sharma



In this tutorial, you will learn how you can handle an error or a promise rejection in JavaScript async/await.

Consider, we have a Promise


const getAsyncOddNumber = (number) => {
  return new Promise((resolve, reject) => {
    setTimeout(()=>{
      if(number<=0) {
        reject('Number must be greater than zero');
      } else {
        if (number % 2 !== 0)
          resolve(`${number} is an odd number`);
        else
          resolve(`${number} is not an odd number`);
      }
    }, 500);
  }) 
}


If the number is less than and equals to zero, then the promise would get rejected, resulting in a JavaScript error.


const mainFn = async () => {
  const message = await getAsyncOddNumber(-2);
  console.log(message); // nothing gets printed
}

mainFn();


To successfully handle the error in async/await, we are going to use JavaScript try...catch statement.


const mainFn = async () => {
  try {
    const message = await getAsyncOddNumber(-2);
    console.log(message);
  } catch(error) {
    console.log(error); // 'Number must be greater than zero'
  }
}

mainFn();


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Suraj Sharma is the founder of Future Gen AI Services. He holds a B.Tech degree in Computer Science & Engineering from NIT Rourkela.