| #nth-check [](https://travis-ci.org/fb55/nth-check) |
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| A performant nth-check parser & compiler. |
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| ###About |
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| 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()`. |
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| `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). |
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| ###API |
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| ```js |
| var nthCheck = require("nth-check"); |
| ``` |
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| #####`nthCheck(formula)` |
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| First parses, then compiles the formula. |
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| #####`nthCheck.parse(formula)` |
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| Parses the expression, throws a `SyntaxError` if it fails, otherwise returns an array containing two elements. |
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| __Example:__ |
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| ```js |
| nthCheck.parse("2n+3") //[2, 3] |
| ``` |
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| #####`nthCheck.compile([a, b])` |
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| Takes an array with two elements (as returned by `.parse`) and returns a highly optimized function. |
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| 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`). |
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| __Example:__ |
| ```js |
| var check = nthCheck.compile([2, 3]); |
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| check(0) //false |
| check(1) //false |
| check(2) //true |
| check(3) //false |
| check(4) //true |
| check(5) //false |
| check(6) //true |
| ``` |
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| --- |
| License: BSD |
