# @vates/predicates [](https://npmjs.org/package/@vates/predicates)  [](https://bundlephobia.com/result?p=@vates/predicates) [](https://npmjs.org/package/@vates/predicates) > Utilities to compose predicates ## Install Installation of the [npm package](https://npmjs.org/package/@vates/predicates): ```sh npm install --save @vates/predicates ``` ## Usage `undefined` predicates are ignored and `undefined` is returned if all predicates are `undefined`, this permits the most efficient composition: ```js const compositePredicate = not(every(undefined, some(not(predicate2), undefined))) // ends up as const compositePredicate = predicate2 ``` Predicates can also be passed wrapped in an array: ```js const compositePredicate = every([predicate1, some([predicate2, predicate3])]) ``` `this` and all arguments are passed to the nested predicates. ### `every(predicates)` > Returns a predicate that returns `true` iff every predicate returns `true`. ```js const isBetween3And7 = every( n => n >= 3, n => n <= 7 ) isBetween3And10(0) // → false isBetween3And10(5) // → true isBetween3And10(10) // → false ``` ### `not(predicate)` > Returns a predicate that returns the negation of the predicate. ```js const isEven = n => n % 2 === 0 const isOdd = not(isEven) isOdd(1) // true isOdd(2) // false ``` ### `some(predicates)` > Returns a predicate that returns `true` iff some predicate returns `true`. ```js const isAliceOrBob = some( name => name === 'Alice', name => name === 'Bob' ) isAliceOrBob('Alice') // → true isAliceOrBob('Bob') // → true isAliceOrBob('Oscar') // → false ``` ## Contributions Contributions are _very_ welcomed, either on the documentation or on the code. You may: - report any [issue](https://github.com/vatesfr/xen-orchestra/issues) you've encountered; - fork and create a pull request. ## License [ISC](https://spdx.org/licenses/ISC) © [Vates SAS](https://vates.fr)