Add support for passing a test

Author: wooorm

index.js

@@ -1,15 +1,24 @@
 'use strict'
 
+var is = require('unist-util-is')
+
 module.exports = size
 
-function size(node) {
+function size(node, test) {
   var children = node && node.children
   var length = (children && children.length) || 0
-  var count = length
+  var count = 0
   var index = -1
+  var child
 
   while (++index < length) {
-    count += size(children[index])
+    child = children[index]
+
+    if (is(test, child, index, node)) {
+      count++
+    }
+
+    count += size(child, test)
   }
 
   return count

package.json

@@ -18,7 +18,9 @@
   "files": [
     "index.js"
   ],
-  "dependencies": {},
+  "dependencies": {
+    "unist-util-is": "^2.1.3"
+  },
   "devDependencies": {
     "browserify": "^16.0.0",
     "hastscript": "^5.0.0",

readme.md

@@ -36,16 +36,25 @@ var tree = h('div', [
 ])
 
 console.log(size(tree)) // => 11
-console.log(size(tree.children[0])) // => 7
-console.log(size(tree.children[0].children[0])) // => 0
+console.log(size(tree, 'element')) // => 5
 ```
 
 ## API
 
-### `size(tree)`
+### `size(tree[, test])`
 
-Calculate the number of nodes in [`node`][node].
-The result is the number of [exclusive descendants][descendant].
+Calculate the number of nodes in [`tree`][node].
+
+###### Parameters
+
+*   `tree` ([`Node`][node]) — [Tree][] to traverse
+*   `test` ([`Test`][is], optional) — [`is`][is]-compatible test (such as a
+    node type)
+
+##### Returns
+
+`number` — Number of [exclusive descendants][descendant] passing `test` in
+`tree`.
 
 ## Contribute
 
@@ -103,6 +112,10 @@ abide by its terms.
 
 [unist]: https://github.com/syntax-tree/unist
 
+[is]: https://github.com/syntax-tree/unist-util-is
+
 [node]: https://github.com/syntax-tree/unist#node
 
+[tree]: https://github.com/syntax-tree/unist#tree
+
 [descendant]: https://github.com/syntax-tree/unist#descendant

test.js

@@ -21,5 +21,7 @@ test('unist-util-size', function(t) {
   t.equal(size(tree.children[0].children[1]), 1, 'parent of text')
   t.equal(size(tree.children[0].children[0]), 0, 'text node')
 
+  t.equal(size(tree, 'element'), 5, 'test')
+
   t.end()
 })