.of and .from methods on collection constructors

Specification
Proposal repo

Modules

esnext.set.of, esnext.set.from, esnext.map.of, esnext.map.from, esnext.weak-set.of, esnext.weak-set.from, esnext.weak-map.of, esnext.weak-map.from

Built-ins signatures

class Set {
  static of(...args: Array<mixed>): Set;
  static from(iterable: Iterable<mixed>, mapFn?: (value: any, index: number) => any, thisArg?: any): Set;
}

class Map {
  static of(...args: Array<[key, value]>): Map;
  static from(iterable: Iterable<mixed>, mapFn?: (value: any, index: number) => [key: any, value: any], thisArg?: any): Map;
}

class WeakSet {
  static of(...args: Array<mixed>): WeakSet;
  static from(iterable: Iterable<mixed>, mapFn?: (value: any, index: number) => Object, thisArg?: any): WeakSet;
}

class WeakMap {
  static of(...args: Array<[key, value]>): WeakMap;
  static from(iterable: Iterable<mixed>, mapFn?: (value: any, index: number) => [key: Object, value: any], thisArg?: any): WeakMap;
}

Entry points

core-js/proposals/collection-of-from
core-js(-pure)/full/set/from
core-js(-pure)/full/set/of
core-js(-pure)/full/map/from
core-js(-pure)/full/map/of
core-js(-pure)/full/weak-set/of
core-js(-pure)/full/weak-set/from
core-js(-pure)/full/weak-map/of
core-js(-pure)/full/weak-map/from

Examples

Set.of(1, 2, 3, 2, 1); // => Set {1, 2, 3}

Map.from([[1, 2], [3, 4]], ([key, value]) => [key ** 2, value ** 2]); // => Map { 1: 4, 9: 16 }