title: Communicate between parent and child renderer process Electron JS
body: <p>Suppose we have the following 2 BrowserWindow instances created in main process:</p>
  
  <pre><code>let fooA = new BrowserWindow({width:800,height:800});
  fooA.loadUrl(url.format({
      pathname: path.join(__dirname, './a.html'),
      protocol: 'file:',
      slashes: true
  }));
  let fooB = new BrowserWindow({parent:fooA});
  fooB.loadUrl(url.format({
      pathname: path.join(__dirname, './b.html'),
      protocol: 'file:',
      slashes: true
  }));
  </code></pre>
  
  <p>As you can see <code>fooB</code> is child of <code>fooA</code>
  Now each browsers window html file is associated with a <code>renderer</code> process:
  <code>fooA</code> is associated with <code>rendererA.js</code> and <code>fooB</code> is associated with <code>rendererB.js</code></p>
  
  <p>Now let's say I want to send a message from <code>rendererA</code> to <code>rendererB</code>
  Do I have to first send a message to main process and the after the main receives it to inform <code>rendererB</code> by using <code>fooB.webContents.send('message-to-b',"rendererA says hello")</code>
  or is there an easier way since <code>fooA</code> is the parent of <code>fooB</code>.</p>