Throwing Errors in Async Context

A typical gotcha in throwing Errors within an Async function

function asyncFunction() {
  setTimeout(function() {
    throw new Error();
  }, 1000)
}

try {
  asyncFunction();
} catch(e) {
  console.log('error occurred')
}

The above will not work because the async callback is not executed in the same context as the try...catch block.

In async contexts, it might be better to use the callback pattern, passing any errors as the first argument in callback:

function asyncFunction(callback) {
  setTimeout(function() {
    callback(new Error());
  }, 2000)
}

asyncFunction(function(err, data) {
  if(err) {
    console.log('error occurred');
    return;
  }
  console.log(data);
})

Posted on: Tue, 22 Jan 2019 09:21:12 GMT

Tags:

nodejs