JSFiddle - React, Tailwind, and code Playground

HTML

<input id="file" type="file" />

JavaScript

const url = 'https://cloud.squidex.io/api/apps/my-tests/assets';
const token = 'YOUR_TOKEN';

const input = document.getElementById('file');

input.addEventListener('change', function () {
  const file = input.files[0];
  
	const formData = new FormData();
  formData.append('file', file);
  fetch(url, {
  	method: 'POST',
    headers: {
    	Authorization: `Bearer ${token}`
    },
    body: formData
  });
});