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: 5a24c314108439a4d4036154
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title: 组合多个 Reducers
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challengeType: 6
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forumTopicId: 301436
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dashedName: combine-multiple-reducers
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---
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# --description--
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当应用程序的状态开始变得越来越复杂时，可能会将 state 分成多个块。 相反，请记住 Redux 的第一个原则：所有应用程序状态都保存在 store 中的一个简单的 state 对象中。 因此，Redux 提供 reducer 组合作为复杂状态模型的解决方案。 定义多个 reducer 来处理应用程序状态的不同部分，然后将这些 reducer 组合成一个 root reducer。 然后将 root reducer 传递给 Redux `createStore()`方法。
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为了将多个 reducer 组合在一起，Redux 提供了`combineReducers()`方法。 该方法接受一个对象作为参数，在该参数中定义一个属性，该属性将键与特定 reducer 函数关联。 Redux 将使用给定的键值作为关联状态的名称。
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通常情况下，当它们在某种程度上是独一无二的，为每个应用程序的 state 创建一个 reducer 是一个很好的做法。 例如，在一个带有用户身份验证的记笔记应用程序中，一个 reducer 可以处理身份验证而另一个处理用户提交的文本和注释。 对于这样的应用程序，可能会编写 `combineReducers()` 方法，如下所示：
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```js
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const rootReducer = Redux.combineReducers({
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auth: authenticationReducer,
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notes: notesReducer
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});
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```
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现在，`notes` 键将包含与注释相关联的所有状态，并由 `notesReducer` 处理。 这就是组合多个 reducer 来管理更复杂的应用程序状态的方式， 在此示例中，Redux store 中保存的状态将是一个包含 `auth` 和 `notes` 属性的简单对象。
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# --instructions--
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代码编辑器中提供了 `counterReducer()` 和 `authReducer()` 函数以及 Redux store。 使用 `Redux.combineReducers()` 方法编写完成 `rootReducer()` 函数。 将 `counterReducer` 分配给一个叫做 `count` 的键，将 `authReducer` 分配给一个叫做 `auth` 的键。
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# --hints--
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`counterReducer` 应该递增和递减 `state`。
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```js
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assert(
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(function () {
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const initialState = store.getState().count;
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store.dispatch({ type: INCREMENT });
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store.dispatch({ type: INCREMENT });
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const firstState = store.getState().count;
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store.dispatch({ type: DECREMENT });
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const secondState = store.getState().count;
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return firstState === initialState + 2 && secondState === firstState - 1;
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})()
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);
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```
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`authReducer` 应该可以使 `authenticated` 的 `state` 值在 `true` 和 `false` 之间切换。
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```js
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assert(
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(function () {
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store.dispatch({ type: LOGIN });
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const loggedIn = store.getState().auth.authenticated;
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store.dispatch({ type: LOGOUT });
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const loggedOut = store.getState().auth.authenticated;
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return loggedIn === true && loggedOut === false;
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})()
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);
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```
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store `state` 应该有两个 key：一个是 `count`，它包含一个数字。 另一个 `auth`，它包含一个对象。 `auth` 对象应该具有 `authenticated` 的属性，该属性的值应该为布尔值。
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```js
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assert(
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(function () {
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const state = store.getState();
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return (
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typeof state.auth === 'object' &&
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typeof state.auth.authenticated === 'boolean' &&
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typeof state.count === 'number'
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);
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})()
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);
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```
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`rootReducer` 应该是一个合并了 `counterReducer` 和 `authReducer` 的函数。
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```js
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(getUserInput) =>
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assert(
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(function () {
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const noWhiteSpace = __helpers.removeWhiteSpace(getUserInput('index'));
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return (
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typeof rootReducer === 'function' &&
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noWhiteSpace.includes('Redux.combineReducers')
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);
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})()
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);
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```
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# --seed--
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## --seed-contents--
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```js
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const INCREMENT = 'INCREMENT';
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const DECREMENT = 'DECREMENT';
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const counterReducer = (state = 0, action) => {
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switch(action.type) {
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case INCREMENT:
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return state + 1;
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case DECREMENT:
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return state - 1;
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default:
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return state;
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}
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};
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const LOGIN = 'LOGIN';
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const LOGOUT = 'LOGOUT';
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const authReducer = (state = {authenticated: false}, action) => {
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switch(action.type) {
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case LOGIN:
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return {
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authenticated: true
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}
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case LOGOUT:
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return {
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authenticated: false
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}
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default:
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return state;
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}
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};
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const rootReducer = // Define the root reducer here
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const store = Redux.createStore(rootReducer);
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```
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# --solutions--
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```js
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const INCREMENT = 'INCREMENT';
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const DECREMENT = 'DECREMENT';
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const counterReducer = (state = 0, action) => {
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switch(action.type) {
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case INCREMENT:
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return state + 1;
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case DECREMENT:
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return state - 1;
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default:
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return state;
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}
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};
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const LOGIN = 'LOGIN';
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const LOGOUT = 'LOGOUT';
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const authReducer = (state = {authenticated: false}, action) => {
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switch(action.type) {
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case LOGIN:
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return {
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authenticated: true
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}
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case LOGOUT:
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return {
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authenticated: false
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}
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default:
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return state;
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}
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};
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const rootReducer = Redux.combineReducers({
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count: counterReducer,
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auth: authReducer
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});
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const store = Redux.createStore(rootReducer);
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```
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