fetch-test.js

fetch('https://jsonplaceholder.typicode.com/posts/1')
  .then(res => {
    const text = res.text();
    console.log(res.bodyUsed);
    // => true
    
    var newResponse = new Response(res.body, res);
    console.log(newResponse.bodyUsed);
    // => `true` if using Chrome, `false` if using Safari, Firefox, or node-fetch
  });