Clarification on paramsSerializer option

[zachlearnscode]

Can anyone provide additional information about the updated paramsSerializer option?

I have a fairly simple use case, where I need a query string with duplicate keys converted from an array value in an object, ie someurl.com?arr=1&arr=2. I've seen this same issue scattered around the docs and discussions, with others bemoaning brackets that appear in a query string.

I am under the impression that setting paramsSerializer to {indexes: null} should correct this issue. Is this correct? If so, what are the reasons that I might be running into errors?

[DigitalBrainJS]

Is this correct?

Yes, this is correct for Axios v1.0.0-alpha.1

  axios.post("https://httpbin.org/post", data, {
    params: {
      foo: "bar",
      arr: [1, 2, 3]
    },
    paramsSerializer: {
      indexes: null
    }
  });

Resolved query string:

post?foo=bar&arr=1&arr=2&arr=3

Playground

Summary:

indexes: null -> post?foo=bar&arr=1&arr=2&arr=3
indexes: false (default) -> post?foo=bar&arr[]=1&arr[]=2&arr[]=3
indexes: true -> post?foo=bar&arr[0]=1&arr[1]=2&arr[2]=3

[zachlearnscode]

Ah, so it is not currently available in .27.x. Thank you!