Set z-index of last used slider handle

.eslintrc

@@ -26,6 +26,9 @@ rules:
     - after-props
   react/require-default-props:
     - 0
+  no-param-reassign:
+    - error
+    - props: false
 env:
   es6: true
   browser: true

src/js/input-range/slider.jsx

@@ -88,6 +88,19 @@ export default class Slider extends React.Component {
     return style;
   }
 
+  /**
+  * set all sibling z-index values to zero
+  * set current node z-index to 2
+  * @private
+  * @return {void}
+  */
+  setZIndex() {
+    this.node.parentElement.childNodes.forEach((child) => {
+      child.style.zIndex = '0';
+    });
+    this.node.style.zIndex = '2';
+  }
+
   /**
    * Listen to mousemove event
    * @private
@@ -176,6 +189,7 @@ export default class Slider extends React.Component {
    */
   @autobind
   handleMouseUp() {
+    this.setZIndex(this.node);
     this.removeDocumentMouseMoveListener();
     this.removeDocumentMouseUpListener();
   }
@@ -216,6 +230,7 @@ export default class Slider extends React.Component {
    */
   @autobind
   handleTouchEnd() {
+    this.setZIndex(this.node);
     this.removeDocumentTouchMoveListener();
     this.removeDocumentTouchEndListener();
   }
@@ -227,6 +242,7 @@ export default class Slider extends React.Component {
    */
   @autobind
   handleKeyDown(event) {
+    this.setZIndex(this.node);
     this.props.onSliderKeyDown(event, this.props.type);
   }
 
@@ -236,7 +252,6 @@ export default class Slider extends React.Component {
    */
   render() {
     const style = this.getStyle();
-
     return (
       <span
         className={this.props.classNames.sliderContainer}