How about no library at all and just use a native XMLHttpRequest instead? Fetch is alright, but it has quite a few shortcomings now and you need a polyfill to even use it across browsers. The specification is in flux and until they address the issues like cancellation and monitoring file upload progress.
var request = new XMLHttpRequest();
request.open('GET', '/api/content', true);
request.onload = function() {
if (this.status >= 200 && this.status < 400) {
var data = JSON.parse(this.response);
} else {
console.error('Response received and there was an error');
}
};
request.onerror = function() {
console.error('Request error');
};
request.send();