Allow walker callback

README.md

@@ -62,6 +62,7 @@ If you either set `escapeHtml` or `skipHtml` to `true`, this component does not
   * `tag` - *string* The resolved tag name for this node
   * `props` - *object* Properties for this tag
   * `children` - *array* Array of unparsed children
+* `walker` - *function* Defines a callback function to walk through all nodes and manipulating them where needed before rendering.
 
 The possible types of elements that can be allowed/disallowed are:
 

src/react-markdown.js

@@ -20,7 +20,8 @@ var ReactMarkdown = React.createClass({
         softBreak: propTypes.string,
         allowNode: propTypes.func,
         allowedTypes: propTypes.array,
-        disallowedTypes: propTypes.array
+        disallowedTypes: propTypes.array,
+        walker: propTypes.func
     },
 
     getDefaultProps: function() {
@@ -34,6 +35,15 @@ var ReactMarkdown = React.createClass({
         var renderer = new ReactRenderer(this.props);
         var ast = parser.parse(this.props.source || '');
 
+        if (this.props.walker) {
+            var walker = ast.walker();
+            var event;
+
+            while ((event = walker.next())) {
+                this.props.walker.call(this, event);
+            }
+        }
+
         if (this.props.className) {
             containerProps.className = this.props.className;
         }

test/react-markdown.test.js

@@ -120,4 +120,19 @@ describe('ReactMarkdown', function() {
 
         expect(ReactDom.findDOMNode(rendered).innerHTML).to.equal('');
     });
+
+    it('allows a walker callback', function() {
+        var walker = function(event) {
+            if (event.entering && event.node.type === 'Strong') {
+                event.node.firstChild.literal = 'walker';
+            }
+        };
+
+        var rendered = TestUtils.renderIntoDocument(
+            React.createElement(ReactMarkdown, { source: testMarkdown, walker: walker })
+        );
+
+        var main = ReactDom.findDOMNode(rendered).innerHTML;
+        expect(main).to.contain('walker</strong>');
+    });
 });