title: reactjs : ShouldComponentUpdate for states
body: <p>How can I use <code>shouldComponentUpdate</code> for states?</p>
  
  <p>I can check: </p>
  
  <pre><code>shouldComponentUpdate(nextProps, nextState) {
    return this.state.value != nextState.value;
  }
  </code></pre>
  
  <p>But it doesn't have any sense for states. Because if I change state(<code>this.setState({value: 'newValue'})</code>) <code>this.state</code> will be equal  <code>nextState</code>.</p>
  
  <p>For example, <code>onClick</code> event:</p>
  
  <pre><code>handleClick() {
    this.setState({value: 'newValue'});
  }
  </code></pre>