add type and node tests

Use unist-util-is for testing a node.

Author: eush77

README.md

@@ -7,6 +7,7 @@
 Create a new [Unist] tree with all nodes that pass the test implemented by the provided function.
 
 [unist]: https://github.com/wooorm/unist
+[unist-util-is]: https://github.com/wooorm/unist-util-is
 
 [travis]: https://travis-ci.org/eush77/unist-util-filter
 [travis-badge]: https://travis-ci.org/eush77/unist-util-filter.svg?branch=master
@@ -78,7 +79,7 @@ filter(ast, (node) => node.type != 'leaf' || node.value % 2 == 0)
 ### `filter(ast, [opts], predicate, [context])`
 
 - `ast` — [Unist] tree.
-- `predicate` — Function to test each node. Invoked with arguments `(node, index?, parent?)`. Return `true` to keep the node, `false` otherwise.
+- `predicate` — Function invoked with arguments `(node, index?, parent?)` or string (type test) or node (identity test) to test each node. See [unist-util-is] for details. In a function form, return `true` to keep the node, `false` otherwise.
 - `context` — Optional. Value to use as `this` when executing `predicate`.
 
 Executes `predicate` for each node in preorder tree traversal. Returns a new tree (or `null`) with nodes for which `predicate` returned `true`.

index.js

@@ -1,18 +1,19 @@
 'use strict';
 
-var flatmap = require('flatmap');
+var flatmap = require('flatmap'),
+    is = require('unist-util-is');
 
 
 module.exports = function (ast, opts, predicate, context) {
-  if (typeof opts == 'function') {
+  if (arguments.length == 2) {
     context = predicate;
     predicate = opts;
     opts = {};
   }
   opts.cascade = opts.cascade || opts.cascade === undefined;
 
   return (function preorder (node, index, parent) {
-    if (!predicate.call(context, node, index, parent)) {
+    if (!is(predicate, node, index, parent, context)) {
       return null;
     }
 

package.json

@@ -27,7 +27,8 @@
     "util"
   ],
   "dependencies": {
-    "flatmap": "0.0.3"
+    "flatmap": "0.0.3",
+    "unist-util-is": "^1.0.0"
   },
   "devDependencies": {
     "tape": "^4.4.0",

test/test.js

@@ -121,3 +121,25 @@ it('should call iterator in a context passed in as the last arg', function (t) {
 
   t.end();
 });
+
+
+it('should support type and node tests', function (t) {
+  var ast = u('node', [
+    u('node', [
+      u('leaf', 1)
+    ]),
+    u('leaf', 2)
+  ]);
+
+  t.equal(filter(ast, 'node'), null);
+
+  t.deepEqual(filter(ast, { cascade: false }, 'node'), u('node', [
+    u('node', [])
+  ]));
+  t.equal(filter(ast, { cascade: false }, 'leaf'), null);
+
+  t.deepEqual(filter(ast, { cascade: false }, ast), u('node', []));
+  t.equal(filter(ast, { cascade: false }, ast.children[0]), null);
+
+  t.end();
+});