Exceptions in asynchronous callbacks in JavaScript

Let, if the number of a non-existent array element is passed as the make parameter, then this is an exceptional situation. As you already know, exceptions thrown inside an async function cannot be caught with try-catch. In our case, an exception thrown inside make or a callback will not be caught:

javascripttry {
  make(10, function(res) {
    console.log(res);
  });
} catch(err) {
  // it won't get caught
}

In the callback approach, they work as follows with exceptions: the result is sent to the first callback parameter, and the error is sent to the second. In this case, the error handling is as follows:

javascriptmake(10, function(res, err) {
  if (!err) {
    console.log(res); // no error occurred, we output the result
  } else {
    console.log(err); // an error has occurred, we output its text
  }
});

Let's rewrite our make function code as described:

javascriptfunction make(num, callback) {
  setTimeout(function() {
    let arr = [1, 2, 3, 4, 5];
    
    let err;
    if (arr[num] === undefined) {
      err = 'elem not exists'; // an error text
    } else {
      err = null; // no error
    }
    
    callback(arr[num], err);
  }, 3000);
}