title: ReactJS send key(index) on click
body: <p>I want to send element's index on click in function. Because I should change data for every element and get it from array.</p>
  
  <p>How can I get key in <code>MainBlock</code> from <code>List</code>? Is it possible? Or I do something wrong?</p>
  
  <p>I'm very new in React and do many mistakes. </p>
  
  <pre><code>var MainBlock = React.createClass({
  Click: function() {
      // I need to get element KEY
      // var data = array[key]
  },
  render: function() {
      return (
          &lt;List Click={this.props.Click.bind(null, this)}&gt;
      );
  }
  });
  
  var List = React.createClass({
      render: function() {
          var ItemNodes = this.props.data.map(function(step, index) {
              return (
                  &lt;Item className="class" Click={this.props.Click.bind(null, this)} key={index} /&gt;
              );
          }.bind(this));
          return (
              &lt;ul&gt;
                  {ItemNodes}
              &lt;/ul&gt;
          );
      }
  });
  
  var StepWindow = React.createClass({
      render: function() {
          return (
              &lt;li onClick={this.props.Click}&gt;
                  yo!
              &lt;/li&gt;
          );
      }
  });
  </code></pre>
  
  <p>Thank you for your help. </p>