S-54545 pull in a fix for setting the element of the modal.

see react-modal >> [fixed] Restore Modal.setAppElement() functionality reactjs#108

Author: darchitetto

lib/components/Modal.js

@@ -5,13 +5,16 @@ var ariaAppHider = require('../helpers/ariaAppHider');
 var injectCSS = require('../helpers/injectCSS');
 
 var SafeHTMLElement = ExecutionEnvironment.canUseDOM ? window.HTMLElement : {};
+var AppElement = ExecutionEnvironment.canUseDOM ? document.body : {appendChild: function() {}};
 
 var Modal = module.exports = React.createClass({
 
   displayName: 'Modal',
 
   statics: {
-    setAppElement: ariaAppHider.setElement,
+    setAppElement: function(element) {
+      AppElement = ariaAppHider.setElement(element);
+    },
     injectCSS: injectCSS
   },
 
@@ -46,7 +49,7 @@ var Modal = module.exports = React.createClass({
   componentDidMount: function() {
     this.node = document.createElement('div');
     this.node.className = 'ReactModalPortal';
-    document.body.appendChild(this.node);
+    AppElement.appendChild(this.node);
     this.renderPortal(this.props);
   },
 
@@ -56,7 +59,7 @@ var Modal = module.exports = React.createClass({
 
   componentWillUnmount: function() {
     React.unmountComponentAtNode(this.node);
-    document.body.removeChild(this.node);
+    AppElement.removeChild(this.node);
   },
 
   renderPortal: function(props) {

lib/helpers/ariaAppHider.js

@@ -1,7 +1,12 @@
 var _element = null;
 
 function setElement(element) {
-  _element = element;
+  if (typeof element === 'string') {
+    var el = document.querySelectorAll(element);
+    element = 'length' in el ? el[0] : el;
+  }
+  _element = element || _element;
+  return _element;
 }
 
 function hide(appElement) {