Files
Shaun Hamilton c2a11ad00d 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>
2021-08-13 21:57:13 -05:00

4.2 KiB

id, title, challengeType, forumTopicId, dashedName
id title challengeType forumTopicId dashedName
5a24c314108439a4d4036174 將 this 綁定到 Class 方法上 6 301379 bind-this-to-a-class-method

--description--

除了設置和更新 state 之外,還可以爲組件類定義方法。 類方法通常需要使用 this 關鍵字,以便它可以訪問方法中類的屬性(例如 stateprops)。 有幾種方法可以讓類方法訪問 this

一種常見的方法是在構造函數中顯式地綁定 this,這樣當組件初始化時,this 就會綁定到類方法。 你可能已經注意到上一個挑戰在構造函數中的 handleClick 方法使用了 this.handleClick = this.handleClick.bind(this)。 然後,當在類方法中調用像 this.setState() 這樣的函數時,this 指的是這個類,而不是 undefined

注意: this關鍵字是 JavaScript 中最令人困惑的方面之一,但它在 React 中扮演着重要的角色。 雖然它的行爲在這裏是完全正常的,但是這些課程並不深入研究this,所以如果以上內容令你感到困惑,請參考其他課程!

--instructions--

代碼編輯器有一個帶有 state 的組件,用於跟蹤項目計數。 它還有一個方法,允許設置文本爲 You clicked!。 但是,該方法不起作用,因爲它使用了未定義的 this 關鍵字。 可以通過將 this 顯式綁定到組件構造函數中的 handleClick()方法來修復它。

接下來,向 render 方法中的 button 元素添加一個單擊處理程序。 當按鈕接收到單擊事件時,它應該觸發 handleClick() 方法。 記住,傳遞給 onClick 處理程序的方法需要使用花括號,因爲它應該直接被解釋爲 JavaScript。

完成上述步驟後,可以單擊按鈕並看到 You clicked!

--hints--

MyComponent 應返回 div 元素,該元素按順序包含兩個元素,一個按鈕和一個 h1 元素。

assert(
  Enzyme.mount(React.createElement(MyComponent)).find('div').length === 1 &&
    Enzyme.mount(React.createElement(MyComponent))
      .find('div')
      .childAt(0)
      .type() === 'button' &&
    Enzyme.mount(React.createElement(MyComponent))
      .find('div')
      .childAt(1)
      .type() === 'h1'
);

MyComponent 的 state 應該使用鍵值對 { text: "Hello" },進行初始化。

assert(
  Enzyme.mount(React.createElement(MyComponent)).state('text') === 'Hello'
);

單擊 button 元素應該運行 handleClick 方法,並使 state textYou clicked!

async () => {
  const waitForIt = (fn) =>
    new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250));
  const mockedComponent = Enzyme.mount(React.createElement(MyComponent));
  const first = () => {
    mockedComponent.setState({ text: 'Hello' });
    return waitForIt(() => mockedComponent.state('text'));
  };
  const second = () => {
    mockedComponent.find('button').simulate('click');
    return waitForIt(() => mockedComponent.state('text'));
  };
  const firstValue = await first();
  const secondValue = await second();
  assert(firstValue === 'Hello' && secondValue === 'You clicked!');
};

--seed--

--after-user-code--

ReactDOM.render(<MyComponent />, document.getElementById('root'))

--seed-contents--

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      text: "Hello"
    };
    // Change code below this line

    // Change code above this line
  }
  handleClick() {
    this.setState({
      text: "You clicked!"
    });
  }
  render() {
    return (
      <div>
        { /* Change code below this line */ }
        <button>Click Me</button>
        { /* Change code above this line */ }
        <h1>{this.state.text}</h1>
      </div>
    );
  }
};

--solutions--

class MyComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      text: "Hello"
    };
    this.handleClick = this.handleClick.bind(this);
  }
  handleClick() {
    this.setState({
      text: "You clicked!"
    });
  }
  render() {
    return (
      <div>
        <button onClick = {this.handleClick}>Click Me</button>
        <h1>{this.state.text}</h1>
      </div>
    );
  }
};