Stuff I wish I’d known sooner about service workers · GitHub

document.querySelector( '.fetch-content' ).addEventListener( 'click', () => {
window.caches.open( myCache )
.then( cache => cache.addAll( content ) )
.then( () => alert( 'content is now available offline' ) )
.catch( () => alert( 'oh noes! something went wrong' ) );
});