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javascript/snippets/reduced-filter.md

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+---
+title: Filter matching and unspecified values
+type: snippet
+tags: [array]
+cover: little-bird
+dateModified: 2020-10-22T20:24:04+03:00
+---
+
+Filters an array of objects based on a condition while also filtering out unspecified keys.
+
+- Use `Array.prototype.filter()` to filter the array based on the predicate `fn` so that it returns the objects for which the condition returned a truthy value.
+- On the filtered array, use `Array.prototype.map()` to return the new object.
+- Use `Array.prototype.reduce()` to filter out the keys which were not supplied as the `keys` argument.
+
+```js
+const reducedFilter = (data, keys, fn) =>
+  data.filter(fn).map(el =>
+    keys.reduce((acc, key) => {
+      acc[key] = el[key];
+      return acc;
+    }, {})
+  );
+```
+
+```js
+const data = [
+  {
+    id: 1,
+    name: 'john',
+    age: 24
+  },
+  {
+    id: 2,
+    name: 'mike',
+    age: 50
+  }
+];
+reducedFilter(data, ['id', 'name'], item => item.age > 24);
+// [{ id: 2, name: 'mike'}]
+```