Error handling for failed network requests with service workers

Most service worker code samples show only the happy path where the fetched resource will eventually be available, eg: self.addEventListener('fetch', event => { // Skip cross-origin requests, like those for Google Analytics. if (event.request.url.startsWith(self.location.origin)) { event.respondWith( caches.match(event.request).then(cachedResponse => { if (cachedResponse) { return cachedResponse; } return caches.open(RUNTIME).then(cache => { return fetch(event.request).then(response => { // Put … Continue reading Error handling for failed network requests with service workers

Book of dark arts: storing data in the view

Pentagram, source Wikipedia. Towards the end of the year I'll indulge in the dark arts, join the goblins and leave my white architect hat under the Christmas tree where it belongs. I'm helping a friend (a technically minded, non-programmer) write his first mobile app . We wanted to keep everything simple: use technologies which can … Continue reading Book of dark arts: storing data in the view

HTTP compression and incremental rendering

TL;DR: HTTP compression can delay rendering of web resources HTTP permits content to be served with different encodings, some of which can be used to compress [1] the data volume transferred over the network, which has become a frequent suggestion [2] towards optimising websites for performance. It turns out that the deflation phase of the … Continue reading HTTP compression and incremental rendering

Secure messaging in the browser

By observing news and public discussions I feel that there is a growing awareness of data privacy and an increasing demand for secure person-to-person communication. In order to address my communication needs, I plugged together a few Javascript libraries and started the Webencryption [1] project on Github. What is Webencryption? Webencryption is a rather crude … Continue reading Secure messaging in the browser

Equal height HTML elements in a container with CSS

Task: create HTML elements that contain other elements and adjust their height to surrounding container. No Javascript allowed. That's surprisingly hard; height:100% won't work; elements generally wrap their contents tightly and don't extend to their parents height dimension. Illustrating the problem: three elements inside a surrounding container Css-tricks lists several ways [1] to get this … Continue reading Equal height HTML elements in a container with CSS

Advanced web security topics

(Last update 28 February 2018) This post discusses web security issues that I come across - so far thankfully mostly by reading about them. It is a work in progress which I'll keep updating. The post title includes "advanced" because the topics discussed here involve clever, non-trivial hacks, are novel at the time of their … Continue reading Advanced web security topics

End-to-end testing Java web applications with an embedded Tomcat

 In this instalment on assembly testing [1] I'll talk about how automated system tests run over my Java web applications. The set-up is rather cheap, not very labour-intensive and can incrementally evolve from a simple assembly test (aka smoke test) to a full-fledged system test. Since this post is rather concrete naming tools and frameworks, … Continue reading End-to-end testing Java web applications with an embedded Tomcat