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- # nth-check [![Build Status](https://travis-ci.org/fb55/nth-check.svg)](https://travis-ci.org/fb55/nth-check)
-
- A performant nth-check parser & compiler.
-
- ### About
-
- This module can be used to parse & compile nth-checks, as they are found in CSS 3's `nth-child()` and `nth-last-of-type()`.
-
- `nth-check` focusses on speed, providing optimized functions for different kinds of nth-child formulas, while still following the [spec](http://www.w3.org/TR/css3-selectors/#nth-child-pseudo).
-
- ### API
-
- ```js
- var nthCheck = require("nth-check");
- ```
-
- ##### `nthCheck(formula)`
-
- First parses, then compiles the formula.
-
- ##### `nthCheck.parse(formula)`
-
- Parses the expression, throws a `SyntaxError` if it fails, otherwise returns an array containing two elements.
-
- __Example:__
-
- ```js
- nthCheck.parse("2n+3") //[2, 3]
- ```
-
- ##### `nthCheck.compile([a, b])`
-
- Takes an array with two elements (as returned by `.parse`) and returns a highly optimized function.
-
- If the formula doesn't match any elements, it returns [`boolbase`](https://github.com/fb55/boolbase)'s `falseFunc`, otherwise, a function accepting an _index_ is returned, which returns whether or not a passed _index_ matches the formula. (Note: The spec starts counting at `1`, the returned function at `0`).
-
- __Example:__
- ```js
- var check = nthCheck.compile([2, 3]);
-
- check(0) //false
- check(1) //false
- check(2) //true
- check(3) //false
- check(4) //true
- check(5) //false
- check(6) //true
- ```
-
- ---
- License: BSD
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