react-ga の pageview をページ遷移毎に発火する with react-router v4 ref: https://qiita.com/moriyuu/items/349fc02dc7e469009b6a

App.js

import React, { Component } from "react";
import { BrowserRouter } from "react-router-dom";
import ReactGA from "react-ga";
import routesGetter from "./Routes";
import { getGaId } from "./utils";

const Analitics = props => {
  ReactGA.pageview(
    props.location.pathname + props.location.search + props.location.hash
  );
  return null;
};

const Routes = routesGetter({ children: Analitics });

class App extends Component {
  constructor() {
    super();

    ReactGA.initialize(getGaId(), { debug: process.env.ENV === "dev" });
  }

  render() {
    return (
      <BrowserRouter>
        <Routes />
      </BrowserRouter>
    );
  }
}

export default App;

Routes.js

import React, { Fragment } from "react";
import { withRouter, Switch, Route } from "react-router-dom";
import PageA from "./PageA";
import PageB from "./PageB";

const routesGetter = ({ children: Children }) => {
  return withRouter(routesProps => {
    return (
      <Fragment>
        <Children {...routesProps} />
        <Switch>
          <Route
            exact
            path="/pages/a"
            render={props => <PageA {...routesProps} {...props} />}
          />
          <Route
            exact
            path="/pages/b"
            render={props => <PageB {...routesProps} {...props} />}
          />
        </Switch>
      </Fragment>
    );
  });
};

export default routesGetter;