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authorruki <waruqi@gmail.com>2018-11-08 00:38:48 +0800
committerruki <waruqi@gmail.com>2018-11-07 21:53:09 +0800
commit26105034da4fcce7ac883c899d781f016559310d (patch)
treec459a5dc4e3aa0972d9919033ece511ce76dd129 /node_modules/nth-check/parse.js
parent2c77f00f1a7ecb6c8192f9c16d3b2001b254a107 (diff)
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diff --git a/node_modules/nth-check/parse.js b/node_modules/nth-check/parse.js
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+module.exports = parse;
+
+//following http://www.w3.org/TR/css3-selectors/#nth-child-pseudo
+
+//[ ['-'|'+']? INTEGER? {N} [ S* ['-'|'+'] S* INTEGER ]?
+var re_nthElement = /^([+\-]?\d*n)?\s*(?:([+\-]?)\s*(\d+))?$/;
+
+/*
+ parses a nth-check formula, returns an array of two numbers
+*/
+function parse(formula){
+ formula = formula.trim().toLowerCase();
+
+ if(formula === "even"){
+ return [2, 0];
+ } else if(formula === "odd"){
+ return [2, 1];
+ } else {
+ var parsed = formula.match(re_nthElement);
+
+ if(!parsed){
+ throw new SyntaxError("n-th rule couldn't be parsed ('" + formula + "')");
+ }
+
+ var a;
+
+ if(parsed[1]){
+ a = parseInt(parsed[1], 10);
+ if(isNaN(a)){
+ if(parsed[1].charAt(0) === "-") a = -1;
+ else a = 1;
+ }
+ } else a = 0;
+
+ return [
+ a,
+ parsed[3] ? parseInt((parsed[2] || "") + parsed[3], 10) : 0
+ ];
+ }
+}