How can I fetch an array of URLs with Promise.all?

by

Yes, Promise.all is the right approach, but you actually need it twice if you want to first fetch all urls and then get all texts from them (which again are promises for the body of the response). So you’d need to do

Promise.all(urls.map(u=>fetch(u))).then(responses =>
    Promise.all(responses.map(res => res.text()))
).then(texts => {
    …
})

Your current code is not working because forEach returns nothing (neither an array nor a promise).

Of course you can simplify that and start with getting the body from each response right after the respective fetch promise fulfilled:

Promise.all(urls.map(url =>
    fetch(url).then(resp => resp.text())
)).then(texts => {
    …
})

or the same thing with await:

const texts = await Promise.all(urls.map(async url => {
  const resp = await fetch(url);
  return resp.text();
}));

More Related Contents:

  1. fetch: Reject promise with JSON error object
  2. using a fetch inside another fetch in javascript
  3. How do I access previous promise results in a .then() chain?
  4. Wait until all promises complete even if some rejected
  5. Can I fire and forget a promise in nodejs (ES7)?
  6. Promise.all: Order of resolved values
  7. Is the Promise constructor callback executed asynchronously?
  8. Is Node.js native Promise.all processing in parallel or sequentially?
  9. What is the order of execution in JavaScript promises?
  10. How can I synchronously determine a JavaScript Promise’s state?
  11. Do I need to return after early resolve/reject?
  12. ES6 Promise.all() error handle – Is .settle() needed? [duplicate]
  13. Resolve Javascript Promise outside the Promise constructor scope
  14. multiple, sequential fetch() Promise
  15. How to check if an object is a Promise?
  16. Should a Promise.reject message be wrapped in Error?
  17. Why can I not throw inside a Promise.catch handler?
  18. What do double brackets mean in javascript and how to access them
  19. What is the difference between “event loop queue” and “job queue”?
  20. What is the best general practice to timeout a function in promise [closed]
  21. How to handle HTTP code 4xx responses in fetch api
  22. What are asynchronous functions in JavaScript? What is “async” and “await” in JavaScript?
  23. What is the intention behind clause 2.2.4 of Promise/A+ spec?
  24. Why does the Promise object block rendering?
  25. Promise and Promise.all(array) executed before array fulfilled [duplicate]
  26. Creating a (ES6) promise without starting to resolve it
  27. Node.js: When to use Promises vs Callbacks
  28. Are JavaScript forever-pending promises bad?
  29. Why does javascript ES6 Promises continue execution after a resolve?
  30. Promise.resolve().then vs setImmediate vs nextTick

Leave a Comment