Merge pull request #1513 from 30-seconds/set-operations

Set operations

snippets/frozenSet.md

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+---
+title: frozenSet
+tags: array,intermediate
+---
+
+Creates a frozen `Set` object.
+
+- Use the `new Set()` constructor to create a new `Set` object from `iterable`.
+- Set the `add`, `delete` and `clear` methods of the newly created object to `undefined`, so that they cannot be used, practically freezing the object.
+
+```js
+const frozenSet = iterable => {
+  const s = new Set(iterable);
+  s.add = undefined;
+  s.delete = undefined;
+  s.clear = undefined;
+  return s;
+};
+```
+
+```js
+frozenSet([1, 2, 3, 1, 2]); 
+// Set { 1, 2, 3, add: undefined, delete: undefined, clear: undefined }
+```

snippets/isDisjoint.md

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+---
+title: isDisjoint
+tags: array,intermediate
+---
+
+Checks if the two iterables are disjointed (have no common values).
+
+- Use the `new Set()` constructor to create a new `Set` object from each iterable.
+- Use `Array.prototype.every()` and `Set.prototype.has()` to check that the two iterables have no common values.
+
+```js
+const isDisjoint = (a, b) => {
+  const sA = new Set(a), sB = new Set(b);
+  return [...sA].every(v => !sB.has(v));
+};
+```
+
+```js
+isDisjoint(new Set([1, 2]), new Set([3, 4])); // true
+isDisjoint(new Set([1, 2]), new Set([1, 3])); // false
+```

snippets/subSet.md

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+---
+title: subSet
+tags: array,intermediate
+---
+
+Checks if the first iterable is a subset of the second one.
+
+- Use the `new Set()` constructor to create a new `Set` object from each iterable.
+- Use `Array.prototype.every()` and `Set.prototype.has()` to check that each value in the first iterable is contained in the second one.
+
+```js
+const subSet = (a, b) => {
+  const sA = new Set(a), sB = new Set(b);
+  return [...sA].every(v => sB.has(v));
+};
+```
+
+```js
+subSet(new Set([1, 2]), new Set([1, 2, 3, 4])); // true
+subSet(new Set([1, 5]), new Set([1, 2, 3, 4])); // false
+```

snippets/superSet.md

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+---
+title: superSet
+tags: array,intermediate
+---
+
+Checks if the first iterable is a superset of the second one.
+
+- Use the `new Set()` constructor to create a new `Set` object from each iterable.
+- Use `Array.prototype.every()` and `Set.prototype.has()` to check that each value in the second iterable is contained in the first one.
+
+```js
+const superSet = (a, b) => {
+  const sA = new Set(a), sB = new Set(b);
+  return [...sB].every(v => sA.has(v));
+};
+```
+
+```js
+superSet(new Set([1, 2, 3, 4]), new Set([1, 2])); // true
+superSet(new Set([1, 2, 3, 4]), new Set([1, 5])); // false
+```