fix(proxySet): fix .symmetricDifference,.isDisjointFrom; add .difference

docs/api/utils/proxySet.mdx

@@ -16,11 +16,12 @@ Native `Sets` store their data in internal slots which are not observable. This
 `proxySet` is useful when you need the functionality of a `Set` but still want to track changes to the data. `proxySet` can be useful if you're wanting to store unique values or if you want to perform mathematical `Set` operations on the data, such as union, intersection, or difference. `proxySet` supports all of the new methods introduced to `Set`:
 
 - `intersection`
-- `isDisjointFrom`
+- `union`
+- `difference`
+- `symmetricDifference`
 - `isSubsetOf`
 - `isSupersetOf`
-- `symmetricDifference`
-- `union`
+- `isDisjointFrom`
 
 You can see a full list of the methods supported by `proxySet` in the [MDN documentation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set).
 

src/vanilla/utils/proxySet.ts

@@ -10,11 +10,12 @@ type InternalProxySet<T> = Set<T> & {
   index: number
   epoch: number
   intersection: (other: Set<T>) => Set<T>
-  isDisjointFrom: (other: Set<T>) => boolean
+  union: (other: Set<T>) => Set<T>
+  difference: (other: Set<T>) => Set<T>
+  symmetricDifference: (other: Set<T>) => Set<T>
   isSubsetOf: (other: Set<T>) => boolean
   isSupersetOf: (other: Set<T>) => boolean
-  symmetricDifference: (other: Set<T>) => Set<T>
-  union: (other: Set<T>) => Set<T>
+  isDisjointFrom: (other: Set<T>) => boolean
 }
 
 /**
@@ -158,13 +159,44 @@ export function proxySet<T>(initialValues?: Iterable<T> | null) {
       }
       return proxySet(resultSet)
     },
-    isDisjointFrom(other: Set<T>): boolean {
+    union(other: Set<T>) {
       this.epoch // touch property for tracking
+      const resultSet = proxySet<T>()
       const otherSet = proxySet<T>(other)
-      return (
-        this.size === other.size &&
-        [...this.values()].every((value) => !otherSet.has(value))
-      )
+      for (const value of this.values()) {
+        resultSet.add(value)
+      }
+      for (const value of otherSet) {
+        resultSet.add(value)
+      }
+      return proxySet(resultSet)
+    },
+    difference(other: Set<T>) {
+      this.epoch // touch property for tracking
+      const resultSet = proxySet<T>()
+      const otherSet = proxySet<T>(other)
+      for (const value of this.values()) {
+        if (!otherSet.has(value)) {
+          resultSet.add(value)
+        }
+      }
+      return proxySet(resultSet)
+    },
+    symmetricDifference(other: Set<T>) {
+      this.epoch // touch property for tracking
+      const resultSet = proxySet<T>()
+      const otherSet = proxySet<T>(other)
+      for (const value of this.values()) {
+        if (!otherSet.has(value)) {
+          resultSet.add(value)
+        }
+      }
+      for (const value of otherSet.values()) {
+        if (!this.has(value)) {
+          resultSet.add(value)
+        }
+      }
+      return proxySet(resultSet)
     },
     isSubsetOf(other: Set<T>) {
       this.epoch // touch property for tracking
@@ -182,28 +214,10 @@ export function proxySet<T>(initialValues?: Iterable<T> | null) {
         [...otherSet].every((value) => this.has(value))
       )
     },
-    symmetricDifference(other: Set<T>) {
-      this.epoch // touch property for tracking
-      const resultSet = proxySet<T>()
-      const otherSet = proxySet<T>(other)
-      for (const value of this.values()) {
-        if (!otherSet.has(value)) {
-          resultSet.add(value)
-        }
-      }
-      return proxySet(resultSet)
-    },
-    union(other: Set<T>) {
+    isDisjointFrom(other: Set<T>): boolean {
       this.epoch // touch property for tracking
-      const resultSet = proxySet<T>()
       const otherSet = proxySet<T>(other)
-      for (const value of this.values()) {
-        resultSet.add(value)
-      }
-      for (const value of otherSet) {
-        resultSet.add(value)
-      }
-      return proxySet(resultSet)
+      return [...this.values()].every((value) => !otherSet.has(value))
     },
   }
 

tests/proxySet.test.tsx

@@ -847,3 +847,99 @@ describe('ui updates - useSnapshot - iterator methods', () => {
     })
   })
 })
+
+// https://github.com/tc39/proposal-set-methods
+describe('proposal set methods', () => {
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/intersection#examples
+  it('.intersection', () => {
+    const odds = proxySet([1, 3, 5, 7, 9])
+    const squares = proxySet([1, 4, 9])
+    const result = odds.intersection(squares) // Set(2) { 1, 9 }
+    expect(result).toEqual(proxySet([1, 9]))
+  })
+
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/union#examples
+  it('.union', () => {
+    const evens = proxySet([2, 4, 6, 8])
+    const squares = proxySet([1, 4, 9])
+    const result = evens.union(squares) // Set(6) { 2, 4, 6, 8, 1, 9 }
+    expect(result).toEqual(proxySet([2, 4, 6, 8, 1, 9]))
+  })
+
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/difference#examples
+  it('.difference', () => {
+    const odds = proxySet([1, 3, 5, 7, 9])
+    const squares = proxySet([1, 4, 9])
+    const result = odds.difference(squares) // Set(3) { 3, 5, 7 }
+    expect(result).toEqual(proxySet([3, 5, 7]))
+  })
+
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/symmetricDifference#examples
+  it('.symmetricDifference', () => {
+    const evens = proxySet([2, 4, 6, 8])
+    const squares = proxySet([1, 4, 9])
+    const result = evens.symmetricDifference(squares) // Set(5) { 2, 6, 8, 1, 9 }
+    expect(result).toEqual(proxySet([2, 6, 8, 1, 9]))
+  })
+
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/isSubsetOf#examples
+  describe('.isSubsetOf', () => {
+    it('The set of multiples of 4 (<20) is a subset of even numbers (<20)', () => {
+      const fours = proxySet([4, 8, 12, 16])
+      const evens = proxySet([2, 4, 6, 8, 10, 12, 14, 16, 18])
+      expect(fours.isSubsetOf(evens)).toBe(true) // true
+    })
+
+    it('The set of prime numbers (<20) is not a subset of all odd numbers (<20), because 2 is prime but not odd', () => {
+      const primes = proxySet([2, 3, 5, 7, 11, 13, 17, 19])
+      const odds = proxySet([3, 5, 7, 9, 11, 13, 15, 17, 19])
+      expect(primes.isSubsetOf(odds)).toBe(false) // false
+    })
+
+    it('Equivalent sets are subsets of each other', () => {
+      const set1 = proxySet([1, 2, 3])
+      const set2 = proxySet([1, 2, 3])
+      expect(set1.isSubsetOf(set2)).toBe(true) // true
+      expect(set2.isSubsetOf(set1)).toBe(true) // true
+    })
+  })
+
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/isSupersetOf#examples
+  describe('.isSupersetOf', () => {
+    it('The set of even numbers (<20) is a superset of multiples of 4 (<20)', () => {
+      const evens = proxySet([2, 4, 6, 8, 10, 12, 14, 16, 18])
+      const fours = proxySet([4, 8, 12, 16])
+      expect(evens.isSupersetOf(fours)).toBe(true) // true
+    })
+
+    it('The set of all odd numbers (<20) is not a superset of prime numbers (<20), because 2 is prime but not odd', () => {
+      const primes = proxySet([2, 3, 5, 7, 11, 13, 17, 19])
+      const odds = proxySet([3, 5, 7, 9, 11, 13, 15, 17, 19])
+      expect(odds.isSupersetOf(primes)).toBe(false) // false
+    })
+
+    it('Equivalent sets are supersets of each other', () => {
+      const set1 = proxySet([1, 2, 3])
+      const set2 = proxySet([1, 2, 3])
+      expect(set1.isSupersetOf(set2)).toBe(true) // true
+      expect(set2.isSupersetOf(set1)).toBe(true) // true
+    })
+  })
+
+  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/isDisjointFrom#examples
+  describe('.isDisjointFrom', () => {
+    it('The set of perfect squares (<20) is disjoint from the set of prime numbers (<20)', () => {
+      // , because a perfect square is by definition decomposable into the product of two integers, while 1 is also not considered a prime number
+      const primes = proxySet([2, 3, 5, 7, 11, 13, 17, 19])
+      const squares = proxySet([1, 4, 9, 16])
+      expect(primes.isDisjointFrom(squares)).toBe(true) // true
+    })
+
+    it('The set of perfect squares (<20) is not disjoint from the set of composite numbers (<20)', () => {
+      // , because all non-1 perfect squares are by definition composite numbers
+      const composites = proxySet([4, 6, 8, 9, 10, 12, 14, 15, 16, 18])
+      const squares = proxySet([1, 4, 9, 16])
+      expect(composites.isDisjointFrom(squares)).toBe(false) // false
+    })
+  })
+})