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snippets/js/s/omit-by.md

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+---
+title: Omit matching object keys
+type: snippet
+language: javascript
+tags: [object]
+cover: leafy-screens
+dateModified: 2020-10-21T21:54:53+03:00
+---
+
+Creates an object composed of the properties the given function returns falsy for.
+
+- Use `Object.keys()` and `Array.prototype.filter()` to remove the keys for which `fn` returns a truthy value.
+- Use `Array.prototype.reduce()` to convert the filtered keys back to an object with the corresponding key-value pairs.
+- The callback function is invoked with two arguments: (value, key).
+
+```js
+const omitBy = (obj, fn) =>
+  Object.keys(obj)
+    .filter(k => !fn(obj[k], k))
+    .reduce((acc, key) => ((acc[key] = obj[key]), acc), {});
+```
+
+```js
+omitBy({ a: 1, b: '2', c: 3 }, x => typeof x === 'number'); // { b: '2' }
+```