Disable background scroll if modal is open

If the modal is opened on top of scrollable content, allow scrolling
only for the opened modal, disabling the scrollable content's scroll.
When closing the modal, restore scrolling functionality and scrolling
position to modal's parent's scrollable content.

src/components/molecules/Modal/Modal.jsx

@@ -56,6 +56,12 @@ class NewModal extends React.Component {
     setTimeout(this.positionModal, 100)
   }
 
+  componentWillReceiveProps(newProps) {
+    if (this.props.isOpen === true && newProps.isOpen === false) {
+      this.handleModalClose()
+    }
+  }
+
   componentWillUpdate() {
     setTimeout(this.positionModal, 100)
   }
@@ -68,6 +74,22 @@ class NewModal extends React.Component {
     setTimeout(this.positionModal, 100)
   }
 
+  handleModalOpen() {
+    this.windowScrollY = window.scrollY
+    document.body.style.top = `${-this.windowScrollY}px`
+    document.body.style.position = 'fixed'
+    document.body.style.width = '100%'
+    document.body.style.height = '100%'
+  }
+
+  handleModalClose() {
+    document.body.style.top = ''
+    document.body.style.position = ''
+    document.body.style.width = ''
+    document.body.style.height = ''
+    window.scroll(0, this.windowScrollY)
+  }
+
   positionModal() {
     let pageNode = this.modalDiv && this.modalDiv.node.firstChild
     let contentNode = pageNode && pageNode.firstChild
@@ -145,6 +167,7 @@ class NewModal extends React.Component {
         contentLabel={this.props.contentLabel || this.props.title}
         style={modalStyle}
         onRequestClose={this.props.onRequestClose}
+        onAfterOpen={() => { this.handleModalOpen() }}
       >
         {this.renderTitle()}
         {children}