クラスとイテレラブル

iterator.js

class Store {
	constructor() {
		this.obj = {}
	}
	get(key) {
		return this.obj[key]
	}
	set(key, val) {
		this.obj[key] = val
	}
	* [Symbol.iterator]() {
		const obj = this.obj
		for (const key of Object.keys(obj)) {
			yield [key, obj[key]]
		}
	}
}

const s = new Store()
s.set('a', 1)
const a = s.get('a')
console.log(a) // => 1
s.set('b', 2)
s.set('c', 3)
for (const v of s) {
	console.log(v)
}
/* =>
[ 'a', 1 ]
[ 'b', 2 ]
[ 'c', 3 ]
*/
console.log(...s);
// => [ 'a', 1 ] [ 'b', 2 ] [ 'c', 3 ]
const [, b, c] = s
console.log(b, c);
// => [ 'b', 2 ] [ 'c', 3 ]