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javascript/snippets/intersection.md

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+---
+title: Array intersection
+type: snippet
+tags: [array]
+cover: red-berries
+dateModified: 2020-10-20T23:02:01+03:00
+---
+
+Returns the elements that exist in both arrays, filtering duplicate values.
+
+- Create a `Set` from `b`, then use `Array.prototype.filter()` on `a` to only keep values contained in `b`.
+
+```js
+const intersection = (a, b) => {
+  const s = new Set(b);
+  return [...new Set(a)].filter(x => s.has(x));
+};
+```
+
+```js
+intersection([1, 2, 3], [4, 3, 2]); // [2, 3]
+```