JSFiddle - React, Tailwind, and code Playground

JavaScript

const urls = [
	'https://dewnuf111111.com/configuration',
	'https://dewnuf222222.com/configuration',
  'https://bcsmania.co.uk/test.json'
];

let obj = {a: 'test'};
let counter = 0;

function ajax(url) {
	// Check for for last URL in the array
	if (counter < urls.length) {
    return fetch(url)
    	.then(response => {
      	// Combine objects
        obj = Object.assign(obj, response.json());
        console.log(urls[counter], obj);
        return Promise.resolve(obj);
      }).catch(error => {
        counter++;
        // Fetch next URL
        ajax(urls[counter]);
      });
  }
}

function getConfigurations() {
  return ajax(urls[counter]);
}

getConfigurations().then((configurations) => {
	console.log('DONE', configurations);
});