[chore] fix inconsistent component state updates (#231)

React component state updates using setState may
asynchronously update this.props and this.state, thus it is
not safe to use either of the two when calculating the new
state passed to setState, and instead the callback-based
variant should be used instead.

Author: s0

examples/selectedKeys.js

@@ -34,9 +34,9 @@ class Test extends React.Component {
   onCheck = (e) => {
     const value = e.target.value;
     if (e.target.checked) {
-      this.setState({
-        selectedKeys: this.state.selectedKeys.concat(value),
-      });
+      this.setState(state => ({
+        selectedKeys: state.selectedKeys.concat(value),
+      }));
     } else {
       const selectedKeys = this.state.selectedKeys.concat();
       const index = selectedKeys.indexOf(value);
@@ -52,9 +52,9 @@ class Test extends React.Component {
   onOpenCheck = (e) => {
     const value = e.target.value;
     if (e.target.checked) {
-      this.setState({
-        openKeys: this.state.openKeys.concat(value),
-      });
+      this.setState(state => ({
+        openKeys: state.openKeys.concat(value),
+      }));
     } else {
       const openKeys = this.state.openKeys.concat();
       const index = openKeys.indexOf(value);