title: Is there any approach to inject or ignore global variables when babel compiling?
body: <p>There is a <code>__DEVTOOLS__</code> global variable in my source code. And normally I use webpack DefinePlugin to define it as boolean value.</p>
  
  <pre><code>new webpack.DefinePlugin({
      __DEVTOOLS__: true
  })
  </code></pre>
  
  <p>But in my mocha test I only want to use <code>babel/register</code> and don't want to use wepack in my test. Is there any approach to inject global variables just like webpack DefinePlugin or at least ignore the global variables when it compile?</p>