AJAX请求池

Question

I have array of FormData objects and I want to post them to same URL. I want to make fixed number of AJAX requests at a time, for that I want to create pool of xhr objects. How to do that?

Answer 1

You can use Array.prototype.splice(), Promise.all(), fetch() to perform N requests at a time.

let data = [FormData, FormData, ..];

let N = 5;

let pool = data.splice(0, N);

let processData = requests => 
  Promise.all(
    requests.map(fd =>
      fetch("/path/to/server", {
        method: "POST",
        body: fd
      })
      .then(response => response.ok)
    )
  )
  .then(responses => responses.every(result => result))
  .then(result => {
    if (result) {
      if (data.length) {
        pool = data.splice(0, N);
        return true
      }
    }
    return "complete"
  });    

let fn = next => next === true ? processData(pool).then(fn) : next;

processData(pool)
.then(fn)
.then(complete => console.log(complete))
.catch(err => console.log(err));

jsfiddle https://jsfiddle.net/ce1kzu52/5/

You can also process the array without scheduling the function processData to be called again if any elements are remaining in array.