feat: add 'back/front end' in curriculum (#42596)
* chore: rename APIs and Microservices to include "Backend" (#42515) * fix typo * fix typo * undo change * Corrected grammar mistake Corrected a grammar mistake by removing a comma. * change APIs and Microservices cert title * update title * Change APIs and Microservices certi title * Update translations.json * update title * feat(curriculum): rename apis and microservices cert * rename folder structure * rename certificate * rename learn Markdown * apis-and-microservices -> back-end-development-and-apis * update backend meta * update i18n langs and cypress test Co-authored-by: Shaun Hamilton <shauhami020@gmail.com> * fix: add development to front-end libraries (#42512) * fix: added-the-word-Development-to-front-end-libraries * fix/added-the-word-Development-to-front-end-libraries * fix/added-word-development-to-front-end-libraries-in-other-related-files * fix/added-the-word-Development-to-front-end-and-all-related-files * fix/removed-typos-from-last-commit-in-index.md * fix/reverted-changes-that-i-made-to-dependecies * fix/removed xvfg * fix/reverted changes that i made to package.json * remove unwanted changes * front-end-development-libraries changes * rename backend certSlug and README * update i18n folder names and keys * test: add legacy path redirect tests This uses serve.json from the client-config repo, since we currently use that in production * fix: create public dir before moving serve.json * fix: add missing script * refactor: collect redirect tests * test: convert to cy.location for stricter tests * rename certificate folder to 00-certificates * change crowdin config to recognise new certificates location * allow translations to be used Co-authored-by: Nicholas Carrigan (he/him) <nhcarrigan@gmail.com> * add forwards slashes to path redirects * fix cypress path tests again * plese cypress * fix: test different challenge Okay so I literally have no idea why this one particular challenge fails in Cypress Firefox ONLY. Tom and I paired and spun a full build instance and confirmed in Firefox the page loads and redirects as expected. Changing to another bootstrap challenge passes Cypress firefox locally. Absolutely boggled by this. AAAAAAAAAAAAAAA * fix: separate the test Okay apparently the test does not work unless we separate it into a different `it` statement. >:( >:( >:( >:( Co-authored-by: Sujal Gupta <55016909+heysujal@users.noreply.github.com> Co-authored-by: Noor Fakhry <65724923+NoorFakhry@users.noreply.github.com> Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com> Co-authored-by: Nicholas Carrigan (he/him) <nhcarrigan@gmail.com>
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---
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id: 5a24c314108439a4d4036178
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title: 创建一个可以控制的输入框
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challengeType: 6
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forumTopicId: 301385
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dashedName: create-a-controlled-input
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---
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# --description--
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应用程序可能在 `state` 和渲染的 UI 之间有更复杂的交互。 例如，用于文本输入的表单控件元素（如 `input` 和 `textarea`）在用户键入时在 DOM 中维护自己的 state。 通过 React，可以将这种可变 state 转移到 React 组件的 `state` 中。 用户的输入变成了应用程序 `state` 的一部分，因此 React 控制该输入字段的值。 通常，如果 React 组件具有用户可以键入的输入字段，那么它将是一个受控的输入表单。
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# --instructions--
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代码编辑器具有一个名为 `ControlledInput` 的组件框架，用于创建受控的 `input` 元素。 组件的 `state` 已经被包含空字符串的 `input` 属性初始化。 此值表示用户在 `input` 字段中键入的文本。
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首先，创建一个名为 `handleChange()` 的方法，该方法具有一个名为 `event` 的参数。 方法被调用时，它接收一个 `event` 对象，该对象包含一个来自 `input` 元素的字符串文本。 可以使用方法内的 `event.target.value` 来访问这个字符串。 用这个新字符串更新组件的`state`的`input`属性。
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在 `render` 方法中的 `h4` 标签之上创建 `input` 元素。 添加一个 `value` 属性，使其等于组件 `state` 的 `input` 属性。 然后将 `onChange()` 事件处理程序设置到 `handleChange()` 方法中。
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在输入框中键入时，文本由 `handleChange()` 方法处理，文本被设置为本地 `state` 中的 `input` 属性，并渲染在页面上的 `input` 框中。 组件 `state` 是输入数据的唯一真实来源。
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最后，不要忘记在构造函数中添加必要的绑定。
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# --hints--
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`ControlledInput` 应该返回包含一个 `input` 标签和 `p` 标签的 `div` 元素。
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```js
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assert(
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Enzyme.mount(React.createElement(ControlledInput))
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.find('div')
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.children()
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.find('input').length === 1 &&
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Enzyme.mount(React.createElement(ControlledInput))
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.find('div')
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.children()
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.find('p').length === 1
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);
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```
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`ControlledInput` 的 state 应该使用设置为空字符串的 `input` 属性初始化。
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```js
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assert.strictEqual(
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Enzyme.mount(React.createElement(ControlledInput)).state('input'),
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''
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);
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```
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Input 元素中的键入值应该更新 input 的 state 和值，并且 `p` 元素应该在输入时呈现 state。
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```js
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async () => {
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const waitForIt = (fn) =>
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new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250));
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const mockedComponent = Enzyme.mount(React.createElement(ControlledInput));
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const _1 = () => {
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mockedComponent.setState({ input: '' });
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return waitForIt(() => mockedComponent.state('input'));
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};
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const _2 = () => {
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mockedComponent
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.find('input')
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.simulate('change', { target: { value: 'TestInput' } });
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return waitForIt(() => ({
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state: mockedComponent.state('input'),
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text: mockedComponent.find('p').text(),
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inputVal: mockedComponent.find('input').props().value
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}));
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};
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const before = await _1();
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const after = await _2();
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assert(
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before === '' &&
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after.state === 'TestInput' &&
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after.text === 'TestInput' &&
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after.inputVal === 'TestInput'
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);
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};
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```
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# --seed--
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## --after-user-code--
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```jsx
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ReactDOM.render(<ControlledInput />, document.getElementById('root'))
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```
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## --seed-contents--
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```jsx
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class ControlledInput extends React.Component {
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constructor(props) {
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super(props);
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this.state = {
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input: ''
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};
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// Change code below this line
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// Change code above this line
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}
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// Change code below this line
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// Change code above this line
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render() {
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return (
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<div>
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{ /* Change code below this line */}
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{ /* Change code above this line */}
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<h4>Controlled Input:</h4>
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<p>{this.state.input}</p>
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</div>
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);
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}
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};
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```
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# --solutions--
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```jsx
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class ControlledInput extends React.Component {
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constructor(props) {
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super(props);
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this.state = {
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input: ''
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};
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this.handleChange = this.handleChange.bind(this);
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}
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handleChange(event) {
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this.setState({
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input: event.target.value
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});
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}
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render() {
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return (
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<div>
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<input
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value={this.state.input}
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onChange={this.handleChange} />
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<h4>Controlled Input:</h4>
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<p>{this.state.input}</p>
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</div>
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);
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}
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};
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```
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