componentDidMount没有更新我的状态？

Question

我是新来的反应，我只是制作一个查看计数器的各种divs.For我需要div和scrollTop height.But的高度，但获得后，我必须设置valuesstd值。但它不工作。

var React = require('react'); 
var ReactDOM = require('react-dom'); 
var NewsDetail = require('./news-details'); 
var $ = require('jquery'); 
module.exports = React.createClass({ 
     getInitialState: function() { 
     return { 
      news: [{ 
      id: "5", 
      data: "I probably am using the wrong I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value terminology here but this is what I'm trying to do. I want to create a map with a value for each key and a value for each key's object. S" 
      }, { 
      id: "6", 
      data: "I probably am using the wrong I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value terminology here but this is what I'm trying to do. I want to create a map with a value for each key and a value for each key's object. S" 
      }, { 
      id: "7", 
      data: "I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value for each key and a value for each key's object. S" 
      }, { 
      id: "8", 
      data: "I probably am using the wrong I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value terminology here but this is what I'm trying to do. I want to create a map with a value for each key and a value for each key's object. S" 
      }, { 
      id: "9", 
      data: "I probably am using the wrong I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value I probably am using the wrong terminology here but this is what I'm trying to do. I want to create a map with a value terminology here but this is what I'm trying to do. I want to create a map with a value for each key and a value for each key's object. S" 
      }, ], 
      length: null, 
      height: 0 
     } 
     }, 
     componentWillMount: function() {}, 
     componentDidMount: function() { 

     console.log(this.state.length) 
     var lengthh = document.getElementById('newscontanier').children.length; 
     console.log(lengthh); 
     if(lengthh != this.state.length) { 
      this.setState({ 
      length: lengthh //Still null 
      }) 
     } 
     }, 
     render: function() { 
     var newsdata = this.state.news.map(function(newss) { 
      return(< NewsDetail key = { 
       newss.id 
       } {...newss 
       } 
       />) 
      }); 
      return(<div className="newscontanier" id="newscontanier">{newsdata}</div>) 
     } 
     }) 

Answer 1

你只是有一个语法错误在这里，除去周围的JSX单引号 -

return (
    <div className="newscontanier" id="newscontanier">{newsdata}</div> 
); 

看到这里的工作副本 - https://jsfiddle.net/69z2wepo/54531/