Data error in ReactJS
<p>I need some validation data. If the input data contains an error - display a message, if not - render component. Why this syntax contains an error (the first block if...else)? Thanks!</p>

<pre><code>var WeatherItem = React.createClass({
  render: function() {
    if({this.props.cityid} == false){
        alert('false');
    }
    else{
    return (
      &lt;div className = "weatherItem"&gt;
      &lt;h2 className = "weatherHeader"&gt; {this.props.type}&lt;/h2&gt;
      &lt;img className = "weatherImg"  src={this.props.src} /&gt;
      &lt;p className = "weatherTemp" &gt;{this.props.temp}{this.props.tempFrom}{this.props.tempTo} C&lt;/p&gt;
      &lt;/div&gt;
      );
    }
  }
});

var WeatherList = React.createClass({
  render: function() {
    var weatherNodes = this.props.data.map(function(weatherItem){
      return (
        &lt;WeatherItem 
        cityid = {weatherItem.cityid}
        type = {weatherItem.type} 
        src = {weatherItem.src} 
        temp = {weatherItem.temp} 
        tempFrom = {weatherItem.tempFrom} 
        tempTo = {weatherItem.tempTo} 
        key = {weatherItem.id}&gt;
        &lt;/WeatherItem&gt;
        );
    });
    return (
      &lt;div className="weatherList"&gt;
      {weatherNodes}
      &lt;/div&gt;
      );
  }
});

ReactDOM.render(
  &lt;WeatherBox url="weather.php" /&gt;,
  document.getElementById('content')
  );
</code></pre>