add :nth-child

Author: eush77

README.md

@@ -61,7 +61,7 @@ That's it!
   - [x] Ends with: `[value$="suffix"]`
 - [ ] Structural pseudo-classes: `paragraph:first-of-type`
   - [x] `:root`
-  - [ ] `:nth-child(2n+1)`
+  - [x] `:nth-child(2n+1)`
   - [ ] `:nth-last-child(2n+1)`
   - [ ] `:nth-of-type(2n+1)`
   - [ ] `:nth-last-of-type(2n+1)`

lib/match-node.js

@@ -4,10 +4,10 @@ module.exports = matchNode;
 
 
 // Match node against a simple selector.
-function matchNode (rule, node, parent) {
+function matchNode (rule, node, nodeIndex, parent) {
   return matchType(rule, node) &&
     matchAttrs(rule, node) &&
-    matchPseudos(rule, node, parent);
+    matchPseudos(rule, node, nodeIndex, parent);
 }
 
 
@@ -58,14 +58,17 @@ function matchAttrs (rule, node) {
 }
 
 
-function matchPseudos (rule, node, parent) {
+function matchPseudos (rule, node, nodeIndex, parent) {
   return !rule.pseudos || rule.pseudos.every(function (pseudo) {
     switch (pseudo.name) {
       case 'root':
         return parent == null;
 
+      case 'nth-child':
+        return pseudo.value(nodeIndex);
+
       case 'not':
-        return !matchNode(pseudo.value.rule, node, parent);
+        return !matchNode(pseudo.value.rule, node, nodeIndex, parent);
 
       default:
         throw Error('Undefined pseudo-class: ' + pseudo.name);

lib/select.js

@@ -41,7 +41,7 @@ select.rule = function (rule, ast) {
   }
 
   function match (rule, node, nodeIndex, parent) {
-    if (matchNode(rule, node, parent)) {
+    if (matchNode(rule, node, nodeIndex, parent)) {
       if (rule.rule) {
         search(rule.rule, node, nodeIndex, parent);
       }

lib/selector.js

@@ -1,12 +1,49 @@
 'use strict';
 
-var Parser = require('css-selector-parser').CssSelectorParser;
+var Parser = require('css-selector-parser').CssSelectorParser,
+    nthCheck = require('nth-check');
 
 
 module.exports = function parseSelector (selector) {
   var parser = new Parser;
   parser.registerNestingOperators('>', '+', '~');
   parser.registerAttrEqualityMods('^', '*', '$');
   parser.registerSelectorPseudos('not');
-  return parser.parse(selector);
+  return compileNthChecks(parser.parse(selector));
 };
+
+
+function compileNthChecks (ast) {
+  if (ast == null) {
+    return ast;
+  }
+
+  switch (ast.type) {
+    case 'selectors':
+      ast.selectors.forEach(compileNthChecks);
+      break;
+
+    case 'ruleSet':
+      compileNthChecks(ast.rule);
+      break;
+
+    case 'rule':
+      if (ast.pseudos) {
+        ast.pseudos.forEach(function (pseudo) {
+          if (pseudo.name == 'nth-child') {
+            pseudo.value = nthCheck(pseudo.value);
+            pseudo.valueType = 'function';
+          }
+        });
+      }
+      if (ast.rule) {
+        compileNthChecks(ast.rule);
+      }
+      break;
+
+    default:
+      throw Error('Undefined AST node: ' + ast.type);
+  }
+
+  return ast;
+}

package.json

@@ -41,7 +41,8 @@
   ],
   "dependencies": {
     "css-selector-parser": "^1.1.0",
-    "debug": "^2.2.0"
+    "debug": "^2.2.0",
+    "nth-check": "^1.0.1"
   },
   "devDependencies": {
     "tape": "^4.2.0"

test/select.js

@@ -139,6 +139,21 @@ test('structural pseudo-classes', function (t) {
     t.end();
   });
 
+  t.test(':nth-child', function (t) {
+    t.deepEqual(select(ast, ':root:nth-child(0)'), []);
+    t.deepEqual(select(ast, ':root:nth-child(n)'), [ast]);
+    t.deepEqual(select(ast, 'root > list:nth-child(2n+5)'),
+                select(ast, 'root > list'));
+    t.deepEqual(select(ast, 'heading:nth-child(even)'), [
+      path(ast, [1]),
+      path(ast, [7])
+    ]);
+    t.deepEqual(select(ast, ':nth-child(3n+2)[type=inlineCode]')
+                .map(function (node) { return node.value }),
+                ['integer', 'proin', 'tan']);
+    t.end();
+  });
+
   t.end();
 });