React.Children的用法详解

object React.Children.map(object children, function fn [, object context])
 
使用方法：
React.Children.map(this.props.children, function (child) {
  return <li>{child}</li>;
})
其他方法
this.props.children.forEach(function (child) {
  return <li>{child}</li>
})

<script type="text/jsx">
 var NotesList = React.createClass({
  render: function() {
   return (
    <ol>
     {
      React.Children.map(this.props.children, function (child) {
          return <li>{child}</li>;
        })
     }
    </ol>
   );
  }
 });
 
 React.render(
  <NotesList>
   <span>hello</span>
   <span>hello</span>
  </NotesList>,
  document.body
 );
</script>

<NotesList>
  <span>hello</span>
  <span>hello</span>
</NotesList>
//返回两个子节点
 
 
<NotesList></NotesList>
//返回undefined
 
 
<NotesList>null</NotesList>
//返回null

render: function() {
  console.log(React.Children.count(this.props.children)); //2
 
  return (
   <ol>
    {
     this.props.children.forEach(function (child) {
       return <li>{child}</li>
     })
    }
   </ol>
  );
 }

<NotesList>
  <span>hello</span>
  <span>hello</span>
</NotesList>
console.log(React.Children.count(this.props.children)); //2
 
<NotesList></NotesList>
console.log(React.Children.count(this.props.children)); //0
 
<NotesList>null</NotesList>
console.log(React.Children.count(this.props.children)); //1

console.log(React.Children.only(this.props.children[0])); 
//输出对象this.props.children[0]