<script>
"use strict";

(async () => {
let response = await fetch('https://api.github.com/repos/javascript-tutorial/en.javascript.info/commits');

// get one header
alert(response.headers.get('Content-Type')); // application/json; charset=utf-8

// iterate over all headers
for (let [key, value] of response.headers) {
  alert(`${key} = ${value}`);
}
})()
</script>