React: Uncaught TypeError: Cannot set property 'ReactFireMixin' of undefined
<p>I'm getting error after adding "reactfire" module in my code.
don't know what is the problem.
here is my code and error image attached.
maybe there is something wrong in usage of "ReactFireMixin".</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="false" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-html lang-html prettyprint-override"><code>var React = require('react');
var Router = require('react-router');
var Repose = require('./Github/Repose');
var UserProfile = require('./Github/UserProfile');
var Notes = require('./Notes/Notes');
var Repose = require('./Github/Repose');
var ReactFireMixin = require('reactfire');
var Firebase = require('firebase');

var Profile = React.createClass({
  mixins:[ReactFireMixin],
  getInitialState: function(){
    return {
      notes: [1,2,3],
      bio: {
        name: 'Ahmed'
      },
      repose: ['a','b','c']
    };
  },
  componentDidMount : function(){
    this.ref = new Firebase('https://github-note-taker-.firebaseio.com/');
    var childRef = this.ref.child(this.props.params.username);
    this.bingAsArray(childRef,'notes')
  },
  componentWillUnmount : function(){
    this.unbind('notes');
  },
  render: function(){
    return(
      &lt;div className="col-xs-12"&gt;
        &lt;div className="col-xs-4"&gt;
          &lt;UserProfile username={this.props.params.username} bio={this.state.bio} /&gt;
        &lt;/div&gt;
        &lt;div className="col-xs-4" &gt;
          &lt;Repose username={this.props.params.username} repose={this.state.repose} /&gt;
        &lt;/div&gt;
        &lt;div className="col-xs-4"&gt;
          &lt;Notes username={this.props.params.username} notes={this.state.notes} /&gt;
        &lt;/div&gt;
      &lt;/div&gt;
    )
  }
});

module.exports = Profile;</code></pre>
</div>
</div>
</p>

<p>Screenshot of Console Error:</p>

<p><a href="https://i.stack.imgur.com/xERO7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xERO7.png" alt="Screenshot of Console Error"></a></p>