entry on `false` behavior

cookbook/13-false-in-jsx tip.md

@@ -0,0 +1,29 @@
+---
+id: false-in-jsx-tip
+title: False in JSX
+layout: cookbook
+permalink: initial-ajax.html
+prev: initial-ajax.html
+---
+
+Here's how `false` renders in different contexts:
+
+Renders as `id="false"`:
+```js
+/** @jsx React.DOM */
+React.renderComponent(<div id={false} />, mountNode);
+```
+
+String "false" as input value:
+```js
+/** @jsx React.DOM */
+React.renderComponent(<input value={false} />, mountNode);
+```
+
+No child:
+```js
+/** @jsx React.DOM */
+React.renderComponent(<div>{false}</div>, mountNode);
+```
+
+The reason why this one doesn't render as the string `"false"` as a `div` child is to allow the more common use-case: `<div>{x > 1 && You have more than one item}</div>`.

cookbook/13-false-in-jsx.md

@@ -0,0 +1,32 @@
+---
+id: false-in-jsx
+title: False in JSX
+layout: cookbook
+permalink: initial-ajax.html
+prev: initial-ajax.html
+---
+
+### Problem
+How does `undefined` and `false` behave as attribute value and as child component?
+
+### Solution
+Renders as `id="false"`:
+```js
+/** @jsx React.DOM */
+React.renderComponent(<div id={false} />, mountNode);
+```
+
+String "false" as input value:
+```js
+/** @jsx React.DOM */
+React.renderComponent(<input value={false} />, mountNode);
+```
+
+No child:
+```js
+/** @jsx React.DOM */
+React.renderComponent(<div>{false}</div>, mountNode);
+```
+
+### Discussion
+The reason why the last one doesn't render as the string `"false"` as a `div` child is to allow the more common use-case: `<div>{x > 1 && You have more than one item}</div>`.