title: Make Checkbox required in reactjs
body: <p>I want to make checkbox mandatory field in react js.</p>
  <p>I am new to reactjs but i have an idea that i should do it using length . Below is the code:</p>
  <pre><code>&lt;CheckboxGroup name=&quot;zones&quot; value={this.state.zones} onChange={this.handleCheckboxChange}&gt;
         {(Checkbox) =&gt; (
           &lt;&gt;
                                                     
              {this.state.zones_to_render_to_render.map((zone, key) =&gt;
                &lt;Col key={key} lg=&quot;10&quot;&gt;
                    &lt;label &gt;
                           &lt;Checkbox value={zone.zone_id} /&gt;{zone.zone_name}
                    &lt;/label&gt;
               &lt;/Col&gt;
                                                              
  
            )}
                                                          
         &lt;/&gt;
       )}
  &lt;/CheckboxGroup&gt;
  </code></pre>
  <p>How to check using length?</p>