axios 请求并行

Question

I had a question days ago, let's imagine we have the following 3 promises:

let promise1 = axios.get(URL1);
let promise2 = axios.get(URL2);
let promise3 = axios.get(URL3);

They will execute asynchronously and return the data with .then() , and let's suppose each of these GET requests take 1.00 seconds.

The total execution of this requests will take 3 seconds right? Is there any way to execute this requests in parallel so that we get the data of the 3 requests in 1 second? Or it's impossible because of the single-threaded language?

Thank you.

Answer 1

As of May 27, 2020 , you should use Promise.all :

Promise.all([axios.get(URL1), axios.get(URL2), axios.get(URL3)])
    .then((responses) => {
        const [url1rest, url2resp, url3resp] = responses;
        // do something
    });

Now deprecated: you can use axios.all in conjunction with axios.spread :

axios.all([axios.get(URL1), axios.get(URL2), axios.get(URL3)])
     .then(axios.spread(url1resp, url2resp, url3resp) {
          // do something
     });

Answer 2

The code you have will execute them in parallel. That's the point of asynchronous functions.

While JavaScript runs on a single event loop (unless you use Workers), asynchronous code is not bound by that loop. That's why the code is asynchronous in the first place.

The responsibility for making the HTTP requests is handed off to code outside of the event loop. This means it can execute in parallel.