title: Two-way binding with checkboxes always returns "on"
body: <p>I'm trying to reproduce a simple two-way binding example in the React.js framework by following this official tutorial: <a href="http://facebook.github.io/react/docs/two-way-binding-helpers.html" rel="noreferrer">"Two-Way Binding Helpers"</a>.</p>
  
  <p>I created a "MyCheckbox" component that looks like this:</p>
  
  <pre><code>var MyCheckbox = React.createClass({
  
      mixins: [React.addons.LinkedStateMixin],
  
      getInitialState: function () {
          return {
              fieldname: '',
              value: this.props.value
          };
      },
  
      render: function () {
          var valueLink = this.linkState('value');
          var me = this;
          var handleChange = function (e) {
              valueLink.requestChange(e.target.value === 'on');
          };
  
          return React.DOM.input({
              type: 'checkbox',
              checked: valueLink.value,
              onChange: handleChange,
          });
      }
  
  });
  </code></pre>
  
  <p>"MyCheckbox" is rendered the following way:</p>
  
  <pre><code>React.renderComponent(MyCheckbox({
      value: false
  }), document.body);
  </code></pre>
  
  <p>When rendering the first time, everything works as expected, if the value is <code>true</code>, the checkbox will be checked, if the value is <code>false</code> then it will not.</p>
  
  <p>If you initialise the checkbox as being unchecked and then check it, everything works fine.</p>
  
  <ul>
  <li><p>The issues it that when clicking the checkbox to uncheck it, <code>e.target.value</code> is always 'on'.</p></li>
  <li><p>I also wanted to ask what differences are there between the <a href="http://facebook.github.io/react/docs/two-way-binding-helpers.html#reactlink-without-linkedstatemixin" rel="noreferrer">ReactLink Without LinkedStateMixin</a> and <a href="http://facebook.github.io/react/docs/two-way-binding-helpers.html#reactlink-without-valuelink" rel="noreferrer">ReactLink Without valueLink</a> methods of data-binding ?</p></li>
  </ul>
  
  <p>Any ideas ?</p>
  
  <p>I use the latest React.js version (<code>v0.10.0</code>).</p>