safe-await.js

// Safe await 
// This is from a brilliant article written by David Wells on a cleaner way to maange async operations in javascript
// here: https://davidwells.io/blog/cleaner-async-await-code-without-try-catch


/* Native Error types https://mzl.la/2Veh3TR */
const nativeExceptions = [
  EvalError, RangeError, ReferenceError, SyntaxError, TypeError, URIError
].filter((except) => typeof except === 'function')

/* Throw native errors. ref: https://bit.ly/2VsoCGE */
function throwNative(error) {
  for (const Exception of nativeExceptions) {
    if (error instanceof Exception) throw error
  }
}

function safeAwait(promise, finallyFunc) {
  return promise.then(data => {
    if (data instanceof Error) {
      throwNative(data)
      return [ data ]
    }
    return [ undefined, data ]
  }).catch(error => {
    throwNative(error)
    return [ error ]
  }).finally(() => {
    if (finallyFunc && typeof finallyFunc === 'function') {
      finallyFunc()
    }
  })
}

// Usage 
async function fooBar() {
  const [ error, data ] = await safeAwait(myPromiseXyz())
  if (error) {
    // handle error, retry, ignore etc.
  }
  return data
}