How to add API key to Axios post request for mailchimp

I'm trying to set up an axios post request to add members to an audience list, but I can't figure out how to add the API key (keeps giving error 401: 'Your request did not include an API key.'). I've tried a bunch of things in the "Authorization" header, like what I put below (also: "Bearer ${mailchimpKey}", "${mailchimpKey}", "Bearer ${mailchimpKey}", "Basic ${mailchimpKey}", and probably more...).

I also don't know what the "username" would be, but "any" worked when I tested the API elsewhere.

Does anyone know how I should set this up?

axios
.post(
  `https://${server}.api.mailchimp.com/3.0/lists/${list_id}/members`,
  {
    email_address: email,
    status: "subscribed",
  },
  {
    "User-Agent": "Request-Promise",
    Connection: "keep-alive",
    Authorization: `Basic any:${mailchimpKey}`,
    // Testing on localhost
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Headers": "Content-Type",
  }
)

If your intention is to use HTTP Basic authentication, just use the Axios auth config option

axios.post(
  `https://${server}.api.mailchimp.com/3.0/lists/${encodeURIComponent(list_id)}/members`,
  {
    email_address: email,
    status: "subscribed",
  },
  {
    auth: {
      username: "anystring",
      password: mailchimpKey
    },
    headers: { // personally, I wouldn't add any extra headers
      "User-agent": "Request-Promise"
    }
  }
)

HTTP Basic auth headers look like

Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQ=

where the string after "Basic" is the Base64 encoded "username:password" string. Axios provides the auth option as a convenience so you don't need to encode the string yourself.

Some other problems you had were:

• Adding request headers outside the headers config option
• Attempting to send Access-Control-Allow-Origin and Access-Control-Allow-Headers as request headers. These are response headers only. Adding them to your request will most likely cause more CORS errors