React JS - Uncaught TypeError： this.props.data.map 不是一个函数

javascript json ajax reactjs

2022-08-30 02:07:01

我正在使用reactjs，并且在尝试显示JSON数据（来自文件或服务器）时似乎无法防止此错误：

Uncaught TypeError: this.props.data.map is not a function

我看过：

React 代码抛出 “TypeError： this.props.data.map is not a function”

React.js this.props.data.map（）不是一个函数

这些都没有帮助我解决问题。在我的页面加载后，我可以验证 this.data.props 不是未定义的（并且确实有一个等同于 JSON 对象的值 - 可以调用），所以当它被 ConversationList 调用时，它似乎没有及时加载。如何确保该方法处理的是 JSON 数据而不是变量？window.foomapundefined

var converter = new Showdown.converter();

var Conversation = React.createClass({
  render: function() {
    var rawMarkup = converter.makeHtml(this.props.children.toString());
    return (
      <div className="conversation panel panel-default">
        <div className="panel-heading">
          <h3 className="panel-title">
            {this.props.id}
            {this.props.last_message_snippet}
            {this.props.other_user_id}
          </h3>
        </div>
        <div className="panel-body">
          <span dangerouslySetInnerHTML={{__html: rawMarkup}} />
        </div>
      </div>
    );
  }
});

var ConversationList = React.createClass({
  render: function() {

    window.foo            = this.props.data;
    var conversationNodes = this.props.data.map(function(conversation, index) {

      return (
        <Conversation id={conversation.id} key={index}>
          last_message_snippet={conversation.last_message_snippet}
          other_user_id={conversation.other_user_id}
        </Conversation>
      );
    });

    return (
      <div className="conversationList">
        {conversationNodes}
      </div>
    );
  }
});

var ConversationBox = React.createClass({
  loadConversationsFromServer: function() {
    return $.ajax({
      url: this.props.url,
      dataType: 'json',
      success: function(data) {
        this.setState({data: data});
      }.bind(this),
      error: function(xhr, status, err) {
        console.error(this.props.url, status, err.toString());
      }.bind(this)
    });
  },
  getInitialState: function() {
    return {data: []};
  },
  componentDidMount: function() {
    this.loadConversationsFromServer();
    setInterval(this.loadConversationsFromServer, this.props.pollInterval);
  },
  render: function() {
    return (
      <div className="conversationBox">
        <h1>Conversations</h1>
        <ConversationList data={this.state.data} />
      </div>
    );
  }
});

$(document).on("page:change", function() {
  var $content = $("#content");
  if ($content.length > 0) {
    React.render(
      <ConversationBox url="/conversations.json" pollInterval={20000} />,
      document.getElementById('content')
    );
  }
})

编辑：添加示例对话.json

注意 - 调用还会返回错误：this.props.data.conversations

var conversationNodes = this.props.data.conversations.map...

返回以下错误：

未捕获的类型错误：无法读取未定义的属性“映射”

以下是 conversations.json：

{"user_has_unread_messages":false,"unread_messages_count":0,"conversations":[{"id":18768,"last_message_snippet":"Lorem ipsum","other_user_id":10193}]}

答案 1

该函数仅在数组上可用。
它看起来不是你期望的格式（它是{}，但你期望的是[]）。.mapdata

this.setState({data: data});

应该是

this.setState({data: data.conversations});

检查“data”的类型，并确保它是一个数组。

修改了代码，并提出了一些建议（propType 验证和 clearInterval）：

var converter = new Showdown.converter();

var Conversation = React.createClass({
  render: function() {
    var rawMarkup = converter.makeHtml(this.props.children.toString());
    return (
      <div className="conversation panel panel-default">
        <div className="panel-heading">
          <h3 className="panel-title">
            {this.props.id}
            {this.props.last_message_snippet}
            {this.props.other_user_id}
          </h3>
        </div>
        <div className="panel-body">
          <span dangerouslySetInnerHTML={{__html: rawMarkup}} />
        </div>
      </div>
    );
  }
});

var ConversationList = React.createClass({
 // Make sure this.props.data is an array
  propTypes: {
    data: React.PropTypes.array.isRequired
  },
  render: function() {

    window.foo            = this.props.data;
    var conversationNodes = this.props.data.map(function(conversation, index) {

      return (
        <Conversation id={conversation.id} key={index}>
          last_message_snippet={conversation.last_message_snippet}
          other_user_id={conversation.other_user_id}
        </Conversation>
      );
    });

    return (
      <div className="conversationList">
        {conversationNodes}
      </div>
    );
  }
});

var ConversationBox = React.createClass({
  loadConversationsFromServer: function() {
    return $.ajax({
      url: this.props.url,
      dataType: 'json',
      success: function(data) {
        this.setState({data: data.conversations});
      }.bind(this),
      error: function(xhr, status, err) {
        console.error(this.props.url, status, err.toString());
      }.bind(this)
    });
  },
  getInitialState: function() {
    return {data: []};
  },

 /* Taken from 
    https://facebook.github.io/react/docs/reusable-components.html#mixins
    clears all intervals after component is unmounted
  */
  componentWillMount: function() {
    this.intervals = [];
  },
  setInterval: function() {
    this.intervals.push(setInterval.apply(null, arguments));
  },
  componentWillUnmount: function() {
    this.intervals.map(clearInterval);
  },

  componentDidMount: function() {
    this.loadConversationsFromServer();
    this.setInterval(this.loadConversationsFromServer, this.props.pollInterval);
  },
  render: function() {
    return (
      <div className="conversationBox">
        <h1>Conversations</h1>
        <ConversationList data={this.state.data} />
      </div>
    );
  }
});

$(document).on("page:change", function() {
  var $content = $("#content");
  if ($content.length > 0) {
    React.render(
      <ConversationBox url="/conversations.json" pollInterval={20000} />,
      document.getElementById('content')
    );
  }
})

答案 2

您需要从中创建一个数组，如下所示：props.data

data = Array.from(props.data);

然后就可以使用功能了data.map()