Javascript Fetch Example. That does JSON and preserves statuscode

fetch_example.js

let url = new URL('some url');

let params = [
  [ 'param_1', 'value' ],
  [ 'param_2', 'value' ]
];

url.search = new URLSearchParams(params).toString();

fetch(
  url,
  {
    method: 'GET',
    headers: {
      'Accept': 'application/json'
    }
  }
)
.then(r => r.json().then(data => ({ status: r.status, headers: r.headers, body: data })))
.then((r) => {
    if (r.status == 200) {
        console.log('Got Data', r.body);
    } else {
        console.log('Error', r.status, r.body);
    }
})