JSFiddle - React, Tailwind, and code Playground

HTML

<button id="a">Fetch w headers - OPTIONS</button>
<button id="b">Fetch w/o headers - no OPTIONS</button>

JavaScript

$('#a').click(function(){
  fetch('https://jsonplaceholder.typicode.com/posts', {
    method: 'get',
    headers: {
      'Accept': 'application/json, text/plain, */*',
      'Content-Type': 'application/json'
    }
  }).then(res=>res.json())
    .then(function(res) {
    console.log(res);   
  });
})


$('#b').click(function(){
  fetch('https://jsonplaceholder.typicode.com/posts', {
    method: 'get',
  }).then(res=>res.json())
    .then(function(res) {
    console.log(res);   
  });
})