Promise constructor with reject call vs throwing error

by

Is there any difference between using reject (in p2) from the Promise api, and throwing an error (in p1) using throw?

Yes, you cannot use throw asynchronously, while reject is a callback. For example, some timeout:

new Promise(_, reject) {
    setTimeout(reject, 1000);
});

Its exactly the same?

No, at least not when other code follows your statement. throw immediately completes the resolver function, while calling reject continues execution normally – after having “marked” the promise as rejected.

Also, engines might provide different exception debugging information if you throw error objects.

For your specific example, you are right that p1 and p2 are indistinguishable from the outside.

More Related Contents:

  1. How do I convert an existing callback API to promises?
  2. Async function returning promise, instead of value
  3. Use async await with Array.map
  4. Why is my asynchronous function returning Promise { } instead of a value?
  5. Correct way to write a non-blocking function in Node.js
  6. How to turn this callback into a promise using async/await?
  7. Correct way to write loops for promise.
  8. Promise – is it possible to force cancel a promise
  9. Basic Javascript promise implementation attempt
  10. When is the body of a Promise executed?
  11. return value after a promise [duplicate]
  12. Why do I need to await an async function when it is not supposedly returning a Promise?
  13. How is a promise/defer library implemented? [closed]
  14. resolving an array of promises from within a parent promise
  15. Using promise function inside Javascript Array map
  16. Are JavaScript Promise asynchronous?
  17. How to return from a Promise’s catch/then block?
  18. How do I wait for a promise to finish before returning the variable of a function?
  19. Debounce function implemented with promises
  20. Is there a way to return early in deferred promise?
  21. When to use promise.all()?
  22. How to promisify Node’s child_process.exec and child_process.execFile functions with Bluebird?
  23. Why does the Promise object block rendering?
  24. When does async function actually return a pending promise?
  25. Async Await map not awaiting async function to complete inside map function before mapping next item
  26. Why does javascript ES6 Promises continue execution after a resolve?
  27. How do you properly promisify request?
  28. Rendering resolved promise value in Ember handlebars template
  29. Implement async/await in sort function of arrays javascript
  30. Promise.resolve().then vs setImmediate vs nextTick

Leave a Comment