React教程：TypeError：无法读取未定义的属性“ props”

Question

我决定学习React，并从正式教程开始。一切都好，直到我达到代码的这种状态：

var CommentBox = React.createClass({
  render: () => {
    return (
      <div className="commentBox">
        <h1> Comments </h1>
        <CommentList />
        <CommentForm />
      </div>
    );
  }
});

var CommentForm = React.createClass({
  render: () => {
    return (
      <div className="commentForm">
        Hello, world! I am a comment form;
      </div>
    );
  }
});

var Comment = React.createClass({
  rawMarkup: () => {
    var rawMarkup = marked(this.props.children.toString(), {sanitize: true});
    return {__html: rawMarkup};
  },

  render: () => {
    return (
      <div className="comment">
        <h2 className="commentAuthor">
          {this.props.author}
        </h2> // <--- [[[[[[ ERROR IS HERE ]]]]]]
        <span dangerouslySetInnerHtml={this.rawMarkup} />
      </div>
    );
  }
});

var CommentList = React.createClass({
  render: () => {
    return (
      <div className="commentList">
        <Comment author="Pete Hunt">This is one comment</Comment>
        <Comment author="Jordan Walke">This is *another* comment yo</Comment>
      </div>
    );
  }
});

ReactDOM.render(
  <CommentBox />,
  document.getElementById('content')
);

当我尝试运行它时，在devtools中出现以下错误：

TypeError：无法读取未定义的属性“ props”

…并且调试器在标记的行处暂停（请参见代码）。当我将鼠标悬停this在时{this.props.author}，我将预览具有props属性和所有内容的对象…

Answer 1

使用函数声明（render() {}或render: function {}）代替箭头函数render: () => {}

var Comment = React.createClass({
  rawMarkup() {
    var rawMarkup = marked(this.props.children.toString(), {sanitize: true});
    return {__html: rawMarkup};
  },

  render() {
    return (
      <div className="comment">
        <h2 className="commentAuthor">
          {this.props.author}
        </h2>
        <span dangerouslySetInnerHtml={this.rawMarkup} />
      </div>
    );
  }
});

Example

一个arrow function相比函数表达式表达具有较短的语法和词汇结合此值（不结合其自身的此，自变量，超级或new.target）。箭头函数始终是匿名的。