There's no particular reason why these properties have to be required

Author: jakezatecky

README.md

@@ -70,11 +70,11 @@ class Widget extends React.Component {
 
 | Property           | Type     | Description                                                                                      | Default     |
 | ------------------ | -------- | ------------------------------------------------------------------------------------------------ | ----------- |
-| `checked`          | array    | **Required**. An array of checked node values.                                                   |             |
-| `expanded`         | array    | **Required**. An array of expanded node values.                                                  |             |
 | `nodes`            | array    | **Required**. Specifies the tree nodes and their children.                                       |             |
-| `onCheck`          | function | **Required**. onCheck handler: `function(checked) {}`                                            |             |
-| `onExpand`         | function | **Required**. onExpand handler: `function(expanded) {}`                                          |             |
+| `checked`          | array    | An array of checked node values.                                                                 | `[]`        |
+| `expanded`         | array    | An array of expanded node values.                                                                | `[]`        |
+| `onCheck`          | function | onCheck handler: `function(checked) {}`                                                          | `() => {}`  |
+| `onExpand`         | function | onExpand handler: `function(expanded) {}`                                                        | `() => {}` |
 | `name`             | string   | Optional name for the hidden `<input>` element.                                                  | `undefined` |
 | `nameAsArray`      | bool     | If true, the hidden `<input>` will encode its values as an array rather than a joined string.    | `false`     |
 | `optimisticToggle` | bool     | If true, toggling a partially-checked node will select all children. If false, it will deselect. | `true`      |

examples/dist/index.js

@@ -6990,25 +6990,27 @@ var Tree = function (_React$Component) {
 }(_react2.default.Component);
 
 Tree.propTypes = {
-	checked: _react2.default.PropTypes.arrayOf(_react2.default.PropTypes.string).isRequired,
-	expanded: _react2.default.PropTypes.arrayOf(_react2.default.PropTypes.string).isRequired,
 	nodes: _react2.default.PropTypes.arrayOf(_react2.default.PropTypes.oneOfType([_react2.default.PropTypes.shape(_nodeShape2.default), _react2.default.PropTypes.shape(_extends({}, _nodeShape2.default, {
 		children: _react2.default.PropTypes.arrayOf(_nodeShape2.default)
 	}))])).isRequired,
-	onCheck: _react2.default.PropTypes.func.isRequired,
-	onExpand: _react2.default.PropTypes.func.isRequired,
 
+	checked: _react2.default.PropTypes.arrayOf(_react2.default.PropTypes.string),
+	expanded: _react2.default.PropTypes.arrayOf(_react2.default.PropTypes.string),
 	name: _react2.default.PropTypes.string,
 	nameAsArray: _react2.default.PropTypes.bool,
-	optimisticToggle: _react2.default.PropTypes.bool
+	optimisticToggle: _react2.default.PropTypes.bool,
+	onCheck: _react2.default.PropTypes.func,
+	onExpand: _react2.default.PropTypes.func
 };
 Tree.defaultProps = {
 	checked: [],
 	expanded: [],
 	name: undefined,
 	nameAsArray: false,
 	nodes: [],
-	optimisticToggle: true
+	optimisticToggle: true,
+	onCheck: function onCheck() {},
+	onExpand: function onExpand() {}
 };
 exports.default = Tree;
 

src/js/Tree.js

@@ -6,8 +6,6 @@ import uniqueDomId from './uniqueDomId';
 
 class Tree extends React.Component {
 	static propTypes = {
-		checked: React.PropTypes.arrayOf(React.PropTypes.string).isRequired,
-		expanded: React.PropTypes.arrayOf(React.PropTypes.string).isRequired,
 		nodes: React.PropTypes.arrayOf(
 			React.PropTypes.oneOfType([
 				React.PropTypes.shape(nodeShape),
@@ -17,12 +15,14 @@ class Tree extends React.Component {
 				}),
 			]),
 		).isRequired,
-		onCheck: React.PropTypes.func.isRequired,
-		onExpand: React.PropTypes.func.isRequired,
 
+		checked: React.PropTypes.arrayOf(React.PropTypes.string),
+		expanded: React.PropTypes.arrayOf(React.PropTypes.string),
 		name: React.PropTypes.string,
 		nameAsArray: React.PropTypes.bool,
 		optimisticToggle: React.PropTypes.bool,
+		onCheck: React.PropTypes.func,
+		onExpand: React.PropTypes.func,
 	};
 
 	static defaultProps = {
@@ -32,6 +32,8 @@ class Tree extends React.Component {
 		nameAsArray: false,
 		nodes: [],
 		optimisticToggle: true,
+		onCheck: () => {},
+		onExpand: () => {},
 	};
 
 	constructor(props) {