2018-10-10 22:03:03 +00:00
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---
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id: 5a24c314108439a4d4036167
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2021-03-05 15:43:24 +00:00
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title: 将 class 组件渲染到 DOM 树
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2018-10-10 22:03:03 +00:00
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challengeType: 6
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2020-09-17 16:13:42 +00:00
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forumTopicId: 301404
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2021-01-13 02:31:00 +00:00
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dashedName: render-a-class-component-to-the-dom
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2018-10-10 22:03:03 +00:00
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---
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2020-12-16 07:37:30 +00:00
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# --description--
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2018-10-10 22:03:03 +00:00
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2021-03-05 15:43:24 +00:00
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还记不记得在之前的挑战中使用 ReactDOM API 将 JSX 元素渲染到 DOM, 这与渲染 React 组件的过程十分相似。 过去的几个挑战主要针对组件和组合,因此渲染是在幕后完成的。 但是,如果不调用 ReactDOM API,编写的任何 React 代码都不会渲染到 DOM。
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2018-10-10 22:03:03 +00:00
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2021-03-05 15:43:24 +00:00
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复习一下语法: `ReactDOM.render(componentToRender, targetNode)`。 第一个参数是要渲染的 React 组件。 第二个参数是要在其中渲染该组件的 DOM 节点。
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2018-10-10 22:03:03 +00:00
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2021-03-05 15:43:24 +00:00
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传递到`ReactDOM.render()` 的React 组件与 JSX 元素略有不同。 对于 JSX 元素,传入的是要渲染的元素的名称。 但是,对于 React 组件,需要使用与渲染嵌套组件相同的语法,例如`ReactDOM.render(<ComponentToRender />, targetNode)`。 此语法用于 ES6 class 组件和函数组件都可以。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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# --instructions--
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2020-09-17 16:13:42 +00:00
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2021-03-05 15:43:24 +00:00
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在后台引入了 `Fruits` 和 `Vegetables` 组件。 将两个组件渲染为 `TypesOfFood` 组件的子组件,然后将 `TypesOfFood` 渲染到 DOM 节点, 在这个挑战中,请渲染到 `id='challenge-node'`的 `div` 中。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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# --hints--
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2018-10-10 22:03:03 +00:00
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2021-03-05 15:43:24 +00:00
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`TypesOfFood` 组件应该返回单个 `div` 元素。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(React.createElement(TypesOfFood));
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return mockedComponent.children().type() === 'div';
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})()
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);
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2018-10-10 22:03:03 +00:00
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```
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2021-03-05 15:43:24 +00:00
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`TypesOfFood` 组件应该在 `h1` 元素之后渲染 `Fruits` 组件。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(React.createElement(TypesOfFood));
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return mockedComponent.children().childAt(1).name() === 'Fruits';
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})()
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);
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2018-10-10 22:03:03 +00:00
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```
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2021-03-05 15:43:24 +00:00
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`TypesOfFood` 组件应该在 `Fruits` 组件之后渲染 `Vegetables` 组件。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(React.createElement(TypesOfFood));
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return mockedComponent.children().childAt(2).name() === 'Vegetables';
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})()
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);
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```
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2018-10-10 22:03:03 +00:00
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2021-03-05 15:43:24 +00:00
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`TypesOfFood` 组件应该渲染到 id 为 `challenge-node` 的 `div`中。
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2020-09-17 16:13:42 +00:00
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2018-10-10 22:03:03 +00:00
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```js
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2020-12-16 07:37:30 +00:00
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assert(
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(function () {
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const html = document.getElementById('challenge-node').childNodes[0]
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.innerHTML;
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2020-09-17 16:13:42 +00:00
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return (
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2020-12-16 07:37:30 +00:00
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html.includes(
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'<div><h2>Fruits:</h2><h4>Non-Citrus:</h4><ul><li>Apples</li><li>Blueberries</li><li>Strawberries</li><li>Bananas</li></ul><h4>Citrus:</h4><ul><li>Lemon</li><li>Lime</li><li>Orange</li><li>Grapefruit</li></ul></div>'
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) &&
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html.includes(
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'<div><h2>Vegetables:</h2><ul><li>Brussel Sprouts</li><li>Broccoli</li><li>Squash</li></ul></div>'
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)
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2020-09-17 16:13:42 +00:00
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);
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2020-12-16 07:37:30 +00:00
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})()
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);
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2018-10-10 22:03:03 +00:00
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```
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2020-08-13 15:24:35 +00:00
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2021-01-13 02:31:00 +00:00
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# --seed--
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## --before-user-code--
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```jsx
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const Fruits = () => {
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return (
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<div>
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<h2>Fruits:</h2>
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<h4>Non-Citrus:</h4>
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<ul>
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<li>Apples</li>
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<li>Blueberries</li>
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<li>Strawberries</li>
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<li>Bananas</li>
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</ul>
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<h4>Citrus:</h4>
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<ul>
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<li>Lemon</li>
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<li>Lime</li>
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<li>Orange</li>
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<li>Grapefruit</li>
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</ul>
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</div>
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);
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};
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const Vegetables = () => {
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return (
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<div>
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<h2>Vegetables:</h2>
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<ul>
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<li>Brussel Sprouts</li>
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<li>Broccoli</li>
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<li>Squash</li>
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</ul>
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</div>
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);
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};
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```
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## --seed-contents--
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```jsx
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class TypesOfFood extends React.Component {
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constructor(props) {
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super(props);
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}
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render() {
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return (
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<div>
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<h1>Types of Food:</h1>
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{/* Change code below this line */}
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{/* Change code above this line */}
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</div>
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);
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}
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};
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// Change code below this line
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```
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2020-12-16 07:37:30 +00:00
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# --solutions--
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2021-01-13 02:31:00 +00:00
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```jsx
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class TypesOfFood extends React.Component {
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constructor(props) {
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super(props);
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}
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render() {
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return (
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<div>
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<h1>Types of Food:</h1>
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{/* Change code below this line */}
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<Fruits />
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<Vegetables />
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{/* Change code above this line */}
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</div>
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);
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}
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};
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// Change code below this line
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ReactDOM.render(<TypesOfFood />, document.getElementById('challenge-node'));
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```
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