The half-edge data structure, used in computational geometry.
I remember when I first discovered it, it drove home the point that choice of data structure can really matter - it made a bunch of problems I'd been working on much easier to solve, as it gave a different way of looking at things.
PureScript isn't just for business logic at all - it has its own UI libraries, React bindings, DOM API bindings, and so on. It is more often used for front-ends than anything else that I've seen.
You only need to use one of spago or bower (spago being the recommended choice now), and that's because npm style dependencies are not suitable for PS.
As for why you'd choose it over TypeScript... well, you'd do so if you want to use a functional language that doesn't allow arbitrary effects and has a sound type system.
I don't know whether this is true or not, but either way, working with Haskell makes my job more enjoyable than if I was writing some other language anyway.
I don't think it's mentioned anywhere in the poster, but it's also perhaps worth noting that this came out of a survey, it wasn't just dreamed up by one person / a few people.
An advantage of using the most general signature possible is it restricts the things you can actually do with the values involved, which can make it easier to provide correct implementations.
There's some work towards that in PureScript: https://github.com/kRITZCREEK/psc-ide provides an interface for multiple editors, seems like Atom, Emacs, Vim and VS are available currently.
The main advantage is when doing something like this is Haskell the code you pass around can't have arbitrary side effects, so you don't actually need to worry so much about where it is called.
"In the most serious crimes [such as] child abduction communications data... is absolutely vital. I love watching, as I probably should stop telling people, crime dramas on the television. There's hardly a crime drama where a crime is solved without using the data of a mobile communications device."
Lifting for strength and lifting for large muscles are actually quite different. It is likely a huge bodybuilder type will be strong relative to the average person, but that's not their primary goal, and correspondingly you can be strong without that look too.
Certainly delete can be useful, but nulling a property has almost the same effect (apart from hasOwnProperty still returning true) - if you're looking at optimising at the level this article is talking about avoiding delete might well be sensible.
I remember when I first discovered it, it drove home the point that choice of data structure can really matter - it made a bunch of problems I'd been working on much easier to solve, as it gave a different way of looking at things.