title: JS bind(), I need two "this" contexts
body: <p>This is a generic JS question.</p>
  
  <p>In React-leaflet, I want to handle events via callbacks. The called function gets the caller (event) context which can be used to do stuff like this.getZoom().</p>
  
  <pre><code>onMoveend={this.moveend}
  
  moveend(e){
      // e is the event target
      var zoomText = this.getZoom();
      // this.setState({zoomText: zoomText});  &lt;-- "this" is the map object, not the my React component.
  }
  </code></pre>
  
  <p>The problem is in the same time I need the react element context to update state and call other methods.</p>
  
  <p>To achive "this.getZoom()" the callback should not be bound, to achive "this.setState(...)" I need to bound the callback to "this".</p>
  
  <p>But how to pass both caller and callback contexts as variables to the callback?</p>
  
  <p>Or may be this type of problem is solved in another way?</p>
  
  <p>See this jsfiddle: <a href="https://jsfiddle.net/nf8k23s7/1/" rel="nofollow">https://jsfiddle.net/nf8k23s7/1/</a></p>