I found a strange situation in ES6. For example, I'm using npm packages `react` and `react-router`. I want to import them to the file:

```
import React from "react";
import { browserHistory } from "react-router";

```

The strange situation is that I need to wrap `browserHistory` in figure brackets, but I don't need to wrap React. What is the reason?

```
import { React } from "react"; // React is undefined
import browserHistory from "react-router"; // browserHistory is undefined

```

What's the reason that I need to customize my import?