add google analytics

frontend/src/withTracker.js

@@ -0,0 +1,39 @@
+import React, { Component } from 'react';
+import ReactGA from 'react-ga';
+
+export default function withTracker(WrappedComponent, options = {}) {
+  const trackPage = (page) => {
+    ReactGA.set({
+      page,
+      ...options
+    });
+    ReactGA.pageview(page);
+  };
+
+  const HOC = class extends Component {
+    componentDidMount() {
+      const {
+        location: { pathname: page }
+      } = this.props;
+      trackPage(page);
+    }
+
+    // eslint-disable-next-line camelcase
+    UNSAFE_componentWillReceiveProps(nextProps) {
+      const {
+        location: { pathname: currentPage }
+      } = this.props;
+      const nextPage = nextProps.location.pathname;
+
+      if (currentPage !== nextPage) {
+        trackPage(nextPage);
+      }
+    }
+
+    render() {
+      return <WrappedComponent {...this.props} />;
+    }
+  };
+
+  return HOC;
+}