Add subSet

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
+```