add :only-child

Author: eush77

README.md

@@ -69,7 +69,7 @@ That's it!
   - [x] `:last-child`
   - [ ] `:first-of-type`
   - [ ] `:last-of-type`
-  - [ ] `:only-child`
+  - [x] `:only-child`
   - [ ] `:only-of-type`
   - [ ] `:empty`
 - [x] Negation pseudo-class: `*:not(paragraph)`

lib/match-node.js

@@ -73,6 +73,9 @@ function matchPseudos (rule, node, nodeIndex, parent) {
       case 'last-child':
         return parent && nodeIndex == parent.children.length - 1;
 
+      case 'only-child':
+        return parent && parent.children.length == 1;
+
       case 'not':
         return !matchNode(pseudo.value.rule, node, nodeIndex, parent);
 

test/select.js

@@ -175,6 +175,15 @@ test('structural pseudo-classes', function (t) {
     t.end();
   });
 
+  t.test(':only-child', function (t) {
+    t.deepEqual(select(ast, ':root:only-child'), []);
+    t.deepEqual(select(ast, 'table:only-child'), []);
+    t.deepEqual(select(ast, ':root > *:not(paragraph) > text:only-child')
+                .map(function (node) { return node.value }),
+                ['Risus pretium quam!', 'Vitae', 'References', 'License']);
+    t.end();
+  });
+
   t.end();
 });