AJAX POST request boilerplate using fetch(). May require polyfill from https://github.com/github/fetch

ajax-fetch-post.js

fetch('https://api-to-call.com/endpoint', {
  method: 'POST',
  body: JSON.stringify({id: '200'})
}).then(response => {
  if (response.ok) {
    return response.json();
  } throw new Error('Request failed!');
}, networkError => console.log(networkError.message)
).then(jsonResponse => jsonResponse)