Prefetch resources example via xhr

prefetch.js

var resources = [
    'https://unpkg.com/react@18/umd/react.production.min.js',
    'https://unpkg.com/react-dom@18/umd/react-dom.production.min.js',
];

/** Apply prefetch for subsequences */
function prefetchResources(resources) {
    for (var i = 0; i < resources.length; i++) {
      var xhrRequest = new XMLHttpRequest();
      xhrRequest.open('GET', resources[i], true);
      xhrRequest.send();
    }
}

/** Validate if the current device has good connection */
function isGoodConection() {
    return !/\slow-2g|2g|3g/.test(navigator.connection.effectiveType);
}

if (isGoodConection()) {
    console.info('Prefetching resources....');
    prefetchResources(resources);
} else {
    console.warn('Skip prefetching resources, the user has poor connection');
}