title: toggle class on multiple elements react
body: <p>I got rendered array of filters, by clicking on element I'm pushing them to <code>selectedProperties</code> array, and also I want to set active class on element if it in array. How to do it properly with react? I got next code</p>
  
  <pre><code>...
  render(){
    const {selectedProperties} = this.state;
    let classnames = classNames('box', {
      'active': '' //what condition apply here to set class?
    });
  return (
    &lt;div className="hotel-filter"&gt;
      &lt;div className="filter-label"&gt;Что для вас важно?&lt;/div&gt;
      &lt;div className="filter-options"&gt;
        &lt;ul className="priorities-boxes"&gt;
          {
            this.state.priorities.map(item =&gt; {
              return (
                &lt;li key={item.id}
                    className={classnames}
                    onClick={(evt) =&gt; this.selectValue(item.id)}&gt;
                  &lt;img src={`/images/filter-icons/${item.icon}`} /&gt;
                  &lt;span&gt;{item.name}&lt;/span&gt;
                &lt;/li&gt;
              )
            })
          }
        &lt;/ul&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  )
  }
  </code></pre>
  
  <p>I'm using classnames utility to add class dynamically but my condition is wrong.  </p>