react-router-context.js

import React, { Component  } from 'react';
import Router, { Route, DefaultRoute, RouteHandler, Link } from 'react-router';

var data = require('./data');

class Item extends Component {

  constructor(props,context) {
      super(props);
      //this.state = this.getStateFromStore();
  }

  render () {
    var params = this.context.router.getCurrentParams();
    var category = data.lookupCategory(params.category);
    var item = data.lookupItem(params.category, params.name);
    return (
      <div>
        <h2>{category.name} / {item.name}</h2>
        <p>Price: ${item.price}</p>
      </div>
    );
  }
}

// why it work but not define inside class
Item.contextTypes = {
  router: React.PropTypes.func.isRequired
}