before.js

import React, { Component, PropTypes } from 'react'
import { render } from 'react-dom'

class Parent extends Component {
  static childContextTypes = {
    someContext1: PropTypes.object,
    someContext2: PropTypes.object
  }
  
  render() {
    return (
      <Stuff>
        {this.props.children}
      </Stuff>
    )
  }
}

class Child extends Component {
  static contextTypes = {
    someContext1: PropTypes.object.isRequired,
    someContext2: PropTypes.object.isRequired
  }
  
  render() {
    console.log('Context:', this.context)
    // -> Object { someContext1: {...}, someContext2: {...} }
    
    console.log('Props:', this.props)
    // -> Object { } (usually some stuff, but we don't care right now)
  }
}

render(
  <Parent>
    <Child />
  </Parent>,
  document.getElementById('root')
)