title: Call to function on react
body: <p>How can I call a function _toggleDropdown or _onWindowClick from another class and file?</p>
  
  <p><strong>DropDown.js</strong></p>
  
  <pre><code>export default class DropDown extends React.Component {
  
    _toggleDropdown(e) {
      e.preventDefault()
      this.setState({
        isActive: !this.state.isActive
      })
    }
  
    _onWindowClick(event) {
      const dropdownElement = findDOMNode(this)
      if (event.target !== dropdownElement &amp;&amp; !dropdownElement.contains(event.target) &amp;&amp; this.state.isActive) {
        this.setState({
          isActive: false
        })
      }
    }
  }
  </code></pre>
  
  <p><strong>Header.js</strong></p>
  
  <pre><code>&lt;a onClick={what???}&gt;test&lt;/a&gt;
  </code></pre>