提示了三个错误，怎么也解决不了，麻烦老师帮忙看一下，非常感谢！

Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in. Check the render method of `RouteMap`.

main.js:358 Warning: Failed prop type: The prop `history` is marked as required in `Router`, but its value is `undefined`.    in Router (created by RouteMap)    in RouteMap

Uncaught TypeError: Cannot read property 'location' of undefined

    at new Router (main.js:8862)

    at main.js:27741

    at measureLifeCyclePerf (main.js:27522)

    at ReactCompositeComponentWrapper._constructComponentWithoutOwner (main.js:27740)

    at ReactCompositeComponentWrapper._constructComponent (main.js:27726)

    at ReactCompositeComponentWrapper.mountComponent (main.js:27634)

    at Object.mountComponent (main.js:4205)

    at ReactCompositeComponentWrapper.performInitialMount (main.js:27817)

    at ReactCompositeComponentWrapper.mountComponent (main.js:27704)

    at Object.mountComponent (main.js:4205)