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feat: add polyfill for new Set methods (union, intersection, difference, symmetricDifference, isSubsetOf, isSupersetOf, isDisjointFrom)
Co-authored-by: mattcosta7 <8616962+mattcosta7@users.noreply.github.com>
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‎src/index.ts‎

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@@ -9,6 +9,7 @@ import * as objectGroupBy from './object-groupby.js'
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import * as mapGroupBy from './map-groupby.js'
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import * as promiseTry from './promise-try.js'
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import * as iteratorHelpers from './iterator-helpers.js'
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import * as setMethods from './set-methods.js'
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let supportsModalPseudo = false
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try {
@@ -61,6 +62,7 @@ export const polyfills = {
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mapGroupBy,
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promiseTry,
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iteratorHelpers,
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setMethods,
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}
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export function isSupported() {

‎src/set-methods.ts‎

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// Set-like interface per TC39 spec: must have has, keys, and size
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interface SetLike<T> {
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has(value: T): boolean
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keys(): IterableIterator<T>
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readonly size: number
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}
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/*#__PURE__*/
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export function union<T>(this: Set<T>, other: SetLike<T>): Set<T> {
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const result = new Set<T>(this)
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for (const value of other.keys()) {
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result.add(value)
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}
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return result
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}
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/*#__PURE__*/
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export function intersection<T>(this: Set<T>, other: SetLike<T>): Set<T> {
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const result = new Set<T>()
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for (const value of this) {
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if (other.has(value)) {
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result.add(value)
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}
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}
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return result
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}
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/*#__PURE__*/
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export function difference<T>(this: Set<T>, other: SetLike<T>): Set<T> {
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const result = new Set<T>()
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for (const value of this) {
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if (!other.has(value)) {
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result.add(value)
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}
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}
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return result
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}
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/*#__PURE__*/
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export function symmetricDifference<T>(this: Set<T>, other: SetLike<T>): Set<T> {
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const result = new Set<T>(this)
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for (const value of other.keys()) {
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if (result.has(value)) {
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result.delete(value)
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} else {
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result.add(value)
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}
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}
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return result
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}
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/*#__PURE__*/
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export function isSubsetOf<T>(this: Set<T>, other: SetLike<T>): boolean {
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if (this.size > other.size) return false
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for (const value of this) {
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if (!other.has(value)) {
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return false
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}
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}
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return true
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}
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/*#__PURE__*/
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export function isSupersetOf<T>(this: Set<T>, other: SetLike<T>): boolean {
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for (const value of other.keys()) {
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if (!this.has(value)) {
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return false
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}
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}
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return true
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}
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/*#__PURE__*/
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export function isDisjointFrom<T>(this: Set<T>, other: SetLike<T>): boolean {
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if (this.size <= other.size) {
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for (const value of this) {
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if (other.has(value)) {
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return false
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}
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}
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} else {
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for (const value of other.keys()) {
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if (this.has(value)) {
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return false
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}
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}
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}
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return true
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}
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/*#__PURE__*/
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export function isSupported(): boolean {
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return (
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'union' in Set.prototype &&
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'intersection' in Set.prototype &&
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'difference' in Set.prototype &&
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'symmetricDifference' in Set.prototype &&
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'isSubsetOf' in Set.prototype &&
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'isSupersetOf' in Set.prototype &&
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'isDisjointFrom' in Set.prototype
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)
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}
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/*#__PURE__*/
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export function isPolyfilled(): boolean {
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const proto = Set.prototype as unknown as Record<string, unknown>
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return (
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'union' in Set.prototype &&
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proto['union'] === union &&
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proto['intersection'] === intersection &&
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proto['difference'] === difference &&
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proto['symmetricDifference'] === symmetricDifference &&
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proto['isSubsetOf'] === isSubsetOf &&
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proto['isSupersetOf'] === isSupersetOf &&
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proto['isDisjointFrom'] === isDisjointFrom
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)
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}
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export function apply(): void {
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if (!isSupported()) {
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Object.assign(Set.prototype, {
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union,
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intersection,
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difference,
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symmetricDifference,
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isSubsetOf,
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isSupersetOf,
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isDisjointFrom,
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})
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}
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}

‎test/set-methods.js‎

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import {expect} from 'chai'
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import {
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apply,
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isPolyfilled,
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isSupported,
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union,
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intersection,
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difference,
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symmetricDifference,
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isSubsetOf,
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isSupersetOf,
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isDisjointFrom,
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} from '../src/set-methods.ts'
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// eslint-disable-next-line i18n-text/no-en
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describe('Set methods', () => {
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it('has standard isSupported, isPolyfilled, apply API', () => {
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expect(isSupported).to.be.a('function')
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expect(isPolyfilled).to.be.a('function')
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expect(apply).to.be.a('function')
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expect(isSupported()).to.be.a('boolean')
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expect(isPolyfilled()).to.equal(false)
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})
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describe('union', () => {
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it('returns a new Set with elements from both sets', () => {
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const a = new Set([1, 2, 3])
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const b = new Set([3, 4, 5])
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const result = union.call(a, b)
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expect(result).to.be.instanceof(Set)
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expect([...result].sort()).to.eql([1, 2, 3, 4, 5])
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})
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it('handles empty sets', () => {
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const a = new Set([1, 2])
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const result = union.call(a, new Set())
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expect([...result].sort()).to.eql([1, 2])
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})
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})
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describe('intersection', () => {
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it('returns a new Set with elements in both sets', () => {
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const a = new Set([1, 2, 3])
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const b = new Set([2, 3, 4])
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const result = intersection.call(a, b)
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expect(result).to.be.instanceof(Set)
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expect([...result].sort()).to.eql([2, 3])
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})
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it('returns empty set when no common elements', () => {
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const a = new Set([1, 2])
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const b = new Set([3, 4])
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const result = intersection.call(a, b)
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expect(result.size).to.equal(0)
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})
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})
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describe('difference', () => {
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it('returns a new Set with elements in this but not other', () => {
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const a = new Set([1, 2, 3])
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const b = new Set([2, 3, 4])
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const result = difference.call(a, b)
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expect(result).to.be.instanceof(Set)
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expect([...result]).to.eql([1])
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})
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it('returns a copy of this when no overlap', () => {
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const a = new Set([1, 2])
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const b = new Set([3, 4])
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const result = difference.call(a, b)
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expect([...result].sort()).to.eql([1, 2])
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})
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})
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describe('symmetricDifference', () => {
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it('returns elements in one set but not both', () => {
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const a = new Set([1, 2, 3])
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const b = new Set([2, 3, 4])
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const result = symmetricDifference.call(a, b)
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expect(result).to.be.instanceof(Set)
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expect([...result].sort()).to.eql([1, 4])
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})
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it('returns empty set for identical sets', () => {
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const a = new Set([1, 2])
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const result = symmetricDifference.call(a, new Set([1, 2]))
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expect(result.size).to.equal(0)
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})
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})
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describe('isSubsetOf', () => {
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it('returns true when all elements are in the other set', () => {
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const a = new Set([1, 2])
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const b = new Set([1, 2, 3])
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expect(isSubsetOf.call(a, b)).to.equal(true)
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})
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it('returns false when some elements are not in the other set', () => {
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const a = new Set([1, 2, 4])
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const b = new Set([1, 2, 3])
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expect(isSubsetOf.call(a, b)).to.equal(false)
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})
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it('returns true for empty set', () => {
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const a = new Set()
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const b = new Set([1, 2])
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expect(isSubsetOf.call(a, b)).to.equal(true)
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})
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})
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describe('isSupersetOf', () => {
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it('returns true when this set contains all elements of other', () => {
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const a = new Set([1, 2, 3])
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const b = new Set([1, 2])
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expect(isSupersetOf.call(a, b)).to.equal(true)
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})
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it('returns false when other has elements not in this', () => {
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const a = new Set([1, 2])
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const b = new Set([1, 2, 3])
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expect(isSupersetOf.call(a, b)).to.equal(false)
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})
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it('returns true when other is empty', () => {
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const a = new Set([1, 2])
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expect(isSupersetOf.call(a, new Set())).to.equal(true)
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})
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})
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describe('isDisjointFrom', () => {
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it('returns true when sets have no common elements', () => {
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const a = new Set([1, 2])
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const b = new Set([3, 4])
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expect(isDisjointFrom.call(a, b)).to.equal(true)
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})
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it('returns false when sets share elements', () => {
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const a = new Set([1, 2, 3])
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const b = new Set([3, 4])
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expect(isDisjointFrom.call(a, b)).to.equal(false)
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})
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it('returns true when either set is empty', () => {
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const a = new Set([1, 2])
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expect(isDisjointFrom.call(a, new Set())).to.equal(true)
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})
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})
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})

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