add :first-child

Author: eush77

README.md

@@ -65,7 +65,7 @@ That's it!
   - [ ] `:nth-last-child(2n+1)`
   - [ ] `:nth-of-type(2n+1)`
   - [ ] `:nth-last-of-type(2n+1)`
-  - [ ] `:first-child`
+  - [x] `:first-child`
   - [ ] `:last-child`
   - [ ] `:first-of-type`
   - [ ] `:last-of-type`

lib/match-node.js

@@ -67,6 +67,9 @@ function matchPseudos (rule, node, nodeIndex, parent) {
       case 'nth-child':
         return pseudo.value(nodeIndex);
 
+      case 'first-child':
+        return nodeIndex == 0;
+
       case 'not':
         return !matchNode(pseudo.value.rule, node, nodeIndex, parent);
 

test/select.js

@@ -154,6 +154,18 @@ test('structural pseudo-classes', function (t) {
     t.end();
   });
 
+  t.test(':first-child', function (t) {
+    t.deepEqual(select(ast, ':root:first-child'), [ast]);
+    t.deepEqual(select(ast, 'heading:first-child'), [path(ast, [0])]);
+    t.deepEqual(select(ast, 'list listItem:first-child [value]:first-child'), [
+      path(ast, [4, 0, 0, 0]),
+      path(ast, [4, 1, 1, 0, 0, 0]),
+      path(ast, [4, 1, 1, 0, 1, 0, 0, 0]),
+      path(ast, [6, 0, 0, 0])
+    ]);
+    t.end();
+  });
+
   t.end();
 });