React.js Conf 2015 - Immutable Data and React

I attacked the modern Javascript approach through first focusing on functional programming. 1. Python + functional programming in Python Python is hardly a pure functional language, but it's lovely and simple and has all the core concepts including list comprehensions. This leads you on to... 2. Haskell If you want to find a pure functional solution to a Python problem, first search for the Haskell one and translate it. Then read Learn You a Haskell [0] which was the funniest programming book I ever read and almost, almost taught me about monads (I had it for a second, then tried to explain it in Python and all was lost) Now you can relax cause the hard bit is done. 3. Read Javascript the Good Parts and only pay attention to the functional programming bits. Suddenly mentions of currying aren't so scary. 4. Work your way through the funfunfunction [1] videos, especially the functional playlist [2] and for added bonus he has videos where he works through the first few chapters of Learn You a Haskell. Then you've got map, reduce, filter all completely under control. Now immutability makes more sense, arrow functions don't look so strange, promises are just friendly monads really and we all love those. Now you've got Immutable.js [3], lodash, underscore all reasonable to understand. React's moaning about state and pure functions makes reasonable sense. 5. Babel really isn't that hard. Just following the Meteor + React tutorial [5] got that all working without me really noticing.

Most functional languages have immutable persistent data structures that don't require a linear copy and are fairly efficient. For example in clojure, sequences are implemented as 32-ary tries so insert/delete/update to any particular index will only cost around sizeOfNode * numParents=32 * log_32(n). This comes with a cost that indexing is now log_32(n) but it's usually a fair price to pay. In javascript, immutable.js implement these same ideas (as least according to these talks where they talk about index tries and hash array mapped tries: [this video] ) If you want native support, javascript engines are actually free to swap out their implementation of arrays! I know they already do depending on whether they think your array is sparse("holey") or not: [link] . I also vaguely recall someone saying that unshift (push to front) is automatically optimized by switching to a deque/circular buffer but I might be remembering wrong. Anyway, they can make these optimizations in a distant future but I don't think do today.