Add isContained

snippets/isContainedIn.md

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+---
+title: isContainedIn
+tags: array,intermediate
+---
+
+Returns `true` if the elements of the first array are contained in the second one regardless of order, `false` otherwise.
+
+Use a `for...of` loop over a `Set` created from the first array.
+Use `Array.prototype.some()` to check if all distinct values are contained in the second array, use `Array.prototype.filter()` to compare the amount of occurences of each distinct value in both arrays.
+Return `false` if the count of any element is greater in the first array than the second one, `true` otherwise.
+
+```js
+const isContainedIn = (a, b) => {
+  for (const v of new Set(a))
+    if (
+      !b.some(e => e === v) || 
+      a.filter(e => e === v).length > b.filter(e => e === v).length
+    )
+      return false;
+  return true;
+}
+```
+
+```js
+isContainedIn([1, 4], [2, 4, 1]); // true
+```