Invalidates ServiceWorkers so that you can fetch your assets freshly.

invalidate.js

/**
 * Invalidates the current `ServiceWorker` running on the page.
 * Why? Because managing a cache is damn hard; and sometimes due to race conditions
 * your assets might get out-of-sync.
 * 
 * This mini snippet checks the version of the app against an uncached resource and
 * invalidates the workers if it finds a mismatch.
 */

if ( navigator.serviceWorker && navigator.serviceWorker.getRegistrations ) {
    const checkCache = () => {
    
    // `get` uses HTTP fetch API; feel free to replace it with your version of fetching a request.
    // version.txt is an “uncached” resource and it only contains the current app version.
    //  
    // Note that certain CDNs can be configured to disregard the query parameters and send
    // you a cached copy no matter what you provide in the querystring. 
    //
    // The random querystring parameter `r` is just a preventative measure;
    // you should also make sure that `version.txt` is not cached by your CDN, proxy servers etc.
    //  
    // Alternatively, you can do url-rewriting as in `version-some-ramdom-stuff` will give you
    // a reliable, uncached version number; that will beat any CDN and proxy caches.
    //
    // So the choice is up to you; just make absolute sure that the response is fresh and
    // **not cached** at all times.
    get( `/version.txt?r=${Math.random()}-${(new Date()).getTime()}` )
        .then( ( res ) => res.text() )
        .then( ( text ) => {
            if ( text.trim() !== process.env.VERSION.trim() ) {
                console.warn( 'version mismatch! unregistering the current service worker' );
                
                navigator.serviceWorker.getRegistrations().then( ( registrations ) => {
                    for( let registration of registrations ) {
                        registration.unregister();
                } } );
              
                return;
            }
            
            console.log( 'Version match' );
        } );
    };

    checkCache();
}