Adding `e.preventDefault()` to `handleSubmit`,

Also added plain `return`, updated text.

docs/tutorial.md

@@ -481,16 +481,17 @@ Let's make the form interactive. When the user submits the form, we should clear
 ```javascript{3-13,16-18}
 // tutorial16.js
 var CommentForm = React.createClass({
-  handleSubmit: function() {
+  handleSubmit: function(e) {
+    e.preventDefault();
     var author = this.refs.author.getDOMNode().value.trim();
     var text = this.refs.text.getDOMNode().value.trim();
     if (!text || !author) {
-      return false;
+      return;
     }
     // TODO: send request to the server
     this.refs.author.getDOMNode().value = '';
     this.refs.text.getDOMNode().value = '';
-    return false;
+    return;
   },
   render: function() {
     return (
@@ -508,7 +509,7 @@ var CommentForm = React.createClass({
 
 React attaches event handlers to components using a camelCase naming convention. We attach an `onSubmit` handler to the form that clears the form fields when the form is submitted with valid input.
 
-We always return `false` from the event handler to prevent the browser's default action of submitting the form. (If you prefer, you can instead take the event as an argument and call `preventDefault()` on it.)
+Call `preventDefault()` on the event to prevent the browser's default action of submitting the form.
 
 ##### Refs
 
@@ -562,16 +563,17 @@ Let's call the callback from the `CommentForm` when the user submits the form:
 ```javascript{6}
 // tutorial18.js
 var CommentForm = React.createClass({
-  handleSubmit: function() {
+  handleSubmit: function(e) {
+    e.preventDefault();
     var author = this.refs.author.getDOMNode().value.trim();
     var text = this.refs.text.getDOMNode().value.trim();
     if (!text || !author) {
-      return false;
+      return;
     }
     this.props.onCommentSubmit({author: author, text: text});
     this.refs.author.getDOMNode().value = '';
     this.refs.text.getDOMNode().value = '';
-    return false;
+    return;
   },
   render: function() {
     return (