Promise catch order explained

promises.js

// Promise catch order explained

// When catch() comes before then() in the promise chain, 
// exceptions that occur in the then() handler will not be caught.

// If the promise rejects, the catch() handler will be called.
// If the catch() handler returns a value or a promise that resolves,
// the then() handler will be called.

mayThrowAnException()
  .catch(handleError)
  .then(handleResponse)

// is the same as

let response = null
try {
  response = await mayThrowAnException()
} catch (err) {
  handleError(err)
}
handleResponse(response)

// When catch() comes after then() in the promise chain,
// exceptions that occur in the then() handler will be caught.

// If the promise rejects, the then() handler will not be called,
// and the catch() handler will be called.

mayThrowAnException()
  .then(handleResponse)
  .catch(handleError)

// is the same as

try {
  const response = await mayThrowAnException()
  handleResponse(response)
} catch (err) {
  handleError(err)
}