Sometimes it’s necessary in Javascript in a browser to find out whether an image object loads correctly. You might do this to check whether a server is responding, or whether it’s blocked by a firewall. In plain HTML you would load the image like this <img src=”/maybe.png” /> then look for the browser’s broken-image indicator visually. You can do this… Read more →
Category: Programming
Stripe Elements data sequence diagram
Stripe.com’s Stripe Elements is a great way to handle payment card information in a way that slows down cybercreeps. It’s secure because customers only enter card numbers into Stripe-furnished iframes, never into forms on the site taking payments via Stripe. Here is the sequence diagram for how Stripe Elements handles data flow Read more →
Plant UML
Software designers sometimes need to present UML sequence diagrams like this one. This kind of thing is absurdly fiddly to draw with most graphics packages. But there’s a language called PlantUML that allows us to write them as text and render them in various software tools, including WordPress with the plugin called PlantUML Renderer. The text for this example is… Read more →
Which iframe posted a message to my window?
What do you do if you have a bunch of different iframes in your web page posting messages? How do you know which iframe a message came from? Even if the iframe document comes from a different origin? This does the trick Read more →