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javascript/snippets/complement.md

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+---
+title: Logical complement
+type: snippet
+tags: [function,logic]
+cover: flower-portrait-10
+dateModified: 2020-09-15T16:28:04+03:00
+---
+
+Returns a function that is the logical complement of the given function, `fn`.
+
+- Use the logical not (`!`) operator on the result of calling `fn` with any supplied `args`.
+
+```js
+const complement = fn => (...args) => !fn(...args);
+```
+
+```js
+const isEven = num => num % 2 === 0;
+const isOdd = complement(isEven);
+isOdd(2); // false
+isOdd(3); // true
+```