Step 5: Make an Access Token Request from Your App

POST /auth/o2/token HTTP/1.1
Host: api.amazon.com
Content-Type: application/x-www-form-urlencoded;charset=UTF-8
grant_type=authorization_code&
code=Amazon.Authorization.code&
client_id=yourClientId&
client_secret=yourClientSecret&
code_verifier=AB12CVEXAMPLE&
redirect_uri=yourRedirectUri&

{
  "access_token": "AmazonAccessToken",
  "expires_in": "3600",
  "refresh_token": "YourRefreshToken",
  "token_type": "bearer"
}

const axios = require('axios');

// Amazon OAuth token request in the backend
const OAuthRequests = (function () {
    const header = {
        "headers": {
            "Content-Type": "application/json"
        }
    };

    const accessTokenBody = function (amazonAuthCode, state) {
        return {
            "grant_type": "authorization_code",
            "code": amazonAuthCode,
            "redirect_uri": config.skillConfig.redirect_uri,
            "client_id": config.skillConfig.client_id,
            "client_secret": config.skillConfig.client_secret,
            "code_verifier": config.skillConfig.code_verifier
        };
    };

    return {
        accessTokenRequest: (authcode, state) => {
            return {
                header: header,
                body: accessTokenBody(authcode, state)
            }
        }
    }
})();

// Request the Amazon access/refresh tokens from the Amazon OAuth token server
function getAccessTokenByAuthcode(amazonAuthCode, state) {
    const accessTokenRequest = OAuthRequests.accessTokenRequest(amazonAuthCode, state);
    return axios.post(config.endpoints.oauthEndpoint, accessTokenRequest.body, accessTokenRequest.header);
}