ES6 offers nice new features:

… but also Sets and Maps!

… aka fancier arrays!

const providers = new Set();

iterable object

providers.add('amazon');
providers.add('netflix');
providers.add('netflix');

providers.delete('netflix');

providers.size; // => 1
providers.has('amazon'); // => true
providers.has('itunes'); // => false

providers.values(); // => {'amazon'}

const countries = ['de', 'us', 'us'];
const countriesSet = new Set(countries);

// or super-short via ES6 destructuring 🚀
const uniqueCountries = [...new Set(countries)];

// => {'de', 'us'} 
// unique values!

… aka minimalistic objects!

const filters = new Map();

filters.set('genres', ['action', 'scifi']);
filters.get('genres');    // => ['action', 'scifi']

filters.has('min_price'); // => false
filters.size; // => 1

(no prototype clutter)

How to handle those iterable objects?!

filters.entries(); // => {['genres', ['action', 'scifi']]}
filters.keys();    // => {'genres'}
filters.values();  // => {['action', 'scifi']}

filters.forEach((value, key) => {
    // do stuff...
});

for ([key, value] of filters) {
    // do stuff...
}

Same story as for WeakSets…

Yes, via polyfill.

Tutorial for maps and sets:

http://2ality.com/2015/01/es6-maps-sets.html

As always: MDN as a reference. 💘

Set

Map

ES6 In Depth: Iterators and the for-of loop​