08-27-周三_17-09-29

node_modules/nth-check/parse.js

@@ -0,0 +1,40 @@
+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
+		];
+	}
+}