React: 通过React.Children访问特定子组件

一、简介

React中提供了很多常用的API，其中有一个React.Children可以用来访问特定组件的子元素。它允许用来统计个数、map映射、循环遍历、转换数组以及显示指定子元素，如下所示：

var React = {

  // Modern

  Children: {

    map: ReactChildren.map, //映射

    forEach: ReactChildren.forEach,//遍历

    count: ReactChildren.count,    //个数

    toArray: ReactChildren.toArray,//转换数组

    only: onlyChild //显示子组件

  },

  Component: ReactComponent,  //组件

  createElement: createElement, //创建节点

  cloneElement: cloneElement,   //克隆节点

  isValidElement: ReactElement.isValidElement, //验证节点

  // Classic

  PropTypes: ReactPropTypes, //类型验证

  createClass: ReactClass.createClass, //创建组件类

  createFactory: createFactory, //创建工厂类

  createMixin: function (mixin) {  //创建视图扩展类

    // Currently a noop. Will be used to validate and trace mixins.

    return mixin;

  },

  // This looks DOM specific but these are actually isomorphic helpers

  // since they are just generating DOM strings.

  DOM: ReactDOMFactories, //节点文档

  version: ReactVersion, //版本号

  // Hook for JSX spread, don't use this for anything else.

  __spread: assign

};

二、使用

需求：根据条件，根组件会选择需要显示的子组件进行展示。

<!DOCTYPE html>

<html>

<head lang="en">

    <meta charset="UTF-8">

    <title>Hello React</title>

    <script src="react/react.js"></script>

    <script src="react/react-dom.js"></script>

    <script src="react/browser.min.js"></script>

</head>

<body>

    <div id="container"></div>

    <script type="text/babel">

        const targetNode = document.getElementById("container");

        //结构赋值，作用域本地化

        const {Children, propTypes} = React;

        const {render} = ReactDOM;

        //过滤函数，通过过滤将不符合条件的子组件去除，只会返回特定的子组件进行显示

        const showChild = (children, child) => Children.toArray(children).filter(c => c.type === child)[];

        //下面是无状态函数式组件，children为根组件的孩子组件数组

        //差劲：子组件

        const PoorChild = ({children}) => Children.only(children);

        //中等：子组件

        const MediumChild = ({children}) => Children.only(children);

        //优秀：子组件

        const GoodChild = ({children}) => Children.only(children);

        //展示：根组件，会根据分数显示对应的孩子组件

        const Display = ({score, children}) => {

            console.log(children);

            if (score>= && score < )  return showChild(children, PoorChild);

            if (score >= && score < ) return showChild(children, MediumChild);

            if (score >= && score <= ) return showChild(children, GoodChild);

        };

        //【0 , 60)：差劲  [60 , 85)：中等 [85 , 100]：优秀

        const score = ;

        render(

                <div>

                    <Display score={score}>

                        <PoorChild>

                            <h1>my score is poor!</h1>

                        </PoorChild>

                        <MediumChild>

                            <h1>my score is medium!</h1>

                        </MediumChild>

                        <GoodChild>

                            <h1>my score is good!</h1>

                        </GoodChild>

                    </Display>

                </div>,

            targetNode

        )

    </script>

</body>

</html>

可以看到三个子组件，只有优秀组件显示出来 :

可以看到子元素数组children的结构如下所示：

巴特西

React: 通过React.Children访问特定子组件

最新文章

热门文章