title: react cannot set property of props of undefined
body: <p>I have a simple component like this</p>
  
  <pre><code>import { Component } from 'react'
  
  export default class SearchList extends Component(){
      constructor(props){
          super(props);
      }
      render(){
          const { placeholder } = this.props;
          return(
              &lt;div className="searchList"&gt;
                  &lt;input type="text" placeholder={placeholder}/&gt;
                  &lt;button&gt;Search&lt;/button&gt;
              &lt;/div&gt;
          )
      }
  }
  </code></pre>
  
  <p>The somewhere I do <code>&lt;SearchList placeholder="Search Area" /&gt;</code></p>
  
  <p>Why I got error of cannot set property of props of undefined?</p>