ES6 WeakMaps, Sets, and WeakSets in Depth

Welcome once again to ES6 – “I can’t take this anymore” – in Depth. New here? Start with A Brief History of ES6 Tooling. Then, make your way through destructuring, template literals, arrow functions, the spread operator and rest parameters, improvements coming to object literals, the new classes sugar on top of prototypes, let, const, and the “Temporal Dead Zone”, iterators, generators, Symbols and Maps. This morning we’ll be discussing three more collection data structures coming in ES6: WeakMap, Set and WeakSet. Like I did in previous articles on the series, I would love to point out that you should probably set up Babel and follow along the examples with either a REPL or the babel-node CLI and a file. That’ll make it so much easier for you to internalize the concepts discussed in the series. If you aren’t the “install things on my computer” kind of human, you might prefer to hop on CodePen and then click on the gear icon for JavaScript – they have a Babel preprocessor which makes trying out ES6 a breeze. Another alternative that’s also quite useful is to use Babel’s online REPL – it’ll show you compiled ES5 code to the right of your ES6 code for quick comparison. Before getting into it, let me shamelessly ask for your support if you’re enjoying my ES6 in Depth series. Your contributions will go towards helping me keep up with the schedule, server bills, keeping me fed, and maintaining Pony Foo as a veritable source of JavaScript goodies. Thanks for reading that, and let’s go into collections now! For a bit of context, you may want to check out the article on iterators – which are closely related to ES6 collections – and the one on spread and rest parameters. Now, let’s pick up where we left off – it’s time for WeakMap.