ReactJS-获取元素的高度

React渲染元素后如何获取元素的高度？

的HTML

<div id="container">
<!-- This element's contents will be replaced with your component. -->
<p>
jnknwqkjnkj<br>
jhiwhiw (this is 36px height)
</p>
</div>

ReactJS

var DivSize = React.createClass({

  render: function() {
    let elHeight = document.getElementById('container').clientHeight
    return <div className="test">Size: <b>{elHeight}px</b> but it should be 18px after the render</div>;
  }
});

ReactDOM.render(
  <DivSize />,
  document.getElementById('container')
);

结果

Size: 36px but it should be 18px after the render

它正在计算渲染之前的容器高度（36像素）。我想获得渲染后的高度。在这种情况下，正确的结果应为18px。jsfiddle