* 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>
5.1 KiB
id, title, challengeType, forumTopicId, dashedName
id | title | challengeType | forumTopicId | dashedName |
---|---|---|---|---|
5a24c314108439a4d4036180 | 使用 shouldComponentUpdate 優化重新渲染 | 6 | 301398 | optimize-re-renders-with-shouldcomponentupdate |
--description--
到目前爲止,如果任何組件接收到新的 state
或新的 props
,它會重新渲染自己及其所有子組件。 這通常是好的。 但是 React 提供了一種生命週期方法,當子組件接收到新的 state
或 props
時,可以調用該方法,並特別聲明組件是否應該更新。 這個方法就是 shouldComponentUpdate()
,它將 nextProps
和 nextState
作爲參數。
這種方法是優化性能的有效方法。 例如,默認行爲是,當組件接收到新的 props
時,即使 props
沒有改變,它也會重新渲染。 可以通過使用 shouldComponentUpdate()
比較 props
來防止這種情況發生。 該方法必須返回一個 boolean
(布爾值),該值告訴 React 是否更新組件。 可以比較當前的 props(this.props
)和下一個 props(nextProps
),以確定你是否需要更新,並相應地返回 true
或 false
。
--instructions--
將 shouldComponentUpdate()
方法添加到名爲 OnlyEvens
的組件中。 目前,該方法返回 true
,因此每次收到新的 props
時,OnlyEvens
都會重新渲染。 修改該方法,以便 OnlyEvens
僅在其新 props 的 value
爲偶數時更新。 單擊 Add
按鈕,在觸發其他生命週期鉤子時,在瀏覽器控制檯中查看事件的順序。
--hints--
Controller
組件應該將 OnlyEvens
組件渲染爲子組件。
assert(
(() => {
const mockedComponent = Enzyme.mount(React.createElement(Controller));
return (
mockedComponent.find('Controller').length === 1 &&
mockedComponent.find('OnlyEvens').length === 1
);
})()
);
應該在 OnlyEvens
組件上定義 shouldComponentUpdate
方法。
assert(
(() => {
const child = React.createElement(OnlyEvens)
.type.prototype.shouldComponentUpdate.toString()
.replace(/s/g, '');
return child !== 'undefined';
})()
);
OnlyEvens
組件應該返回一個 h1
標籤,該標籤渲染 this.props.value
的值。
(() => {
const mockedComponent = Enzyme.mount(React.createElement(Controller));
const first = () => {
mockedComponent.setState({ value: 1000 });
return mockedComponent.find('h1').html();
};
const second = () => {
mockedComponent.setState({ value: 10 });
return mockedComponent.find('h1').html();
};
const firstValue = first();
const secondValue = second();
assert(firstValue === '<h1>1000</h1>' && secondValue === '<h1>10</h1>');
})();
只有在 nextProps.value
爲偶數時,OnlyEvens
纔會重新渲染。
(() => {
const mockedComponent = Enzyme.mount(React.createElement(Controller));
const first = () => {
mockedComponent.setState({ value: 8 });
return mockedComponent.find('h1').text();
};
const second = () => {
mockedComponent.setState({ value: 7 });
return mockedComponent.find('h1').text();
};
const third = () => {
mockedComponent.setState({ value: 42 });
return mockedComponent.find('h1').text();
};
const firstValue = first();
const secondValue = second();
const thirdValue = third();
assert(firstValue === '8' && secondValue === '8' && thirdValue === '42');
})();
--seed--
--after-user-code--
ReactDOM.render(<Controller />, document.getElementById('root'));
--seed-contents--
class OnlyEvens extends React.Component {
constructor(props) {
super(props);
}
shouldComponentUpdate(nextProps, nextState) {
console.log('Should I update?');
// Change code below this line
return true;
// Change code above this line
}
componentDidUpdate() {
console.log('Component re-rendered.');
}
render() {
return <h1>{this.props.value}</h1>;
}
}
class Controller extends React.Component {
constructor(props) {
super(props);
this.state = {
value: 0
};
this.addValue = this.addValue.bind(this);
}
addValue() {
this.setState(state => ({
value: state.value + 1
}));
}
render() {
return (
<div>
<button onClick={this.addValue}>Add</button>
<OnlyEvens value={this.state.value} />
</div>
);
}
}
--solutions--
class OnlyEvens extends React.Component {
constructor(props) {
super(props);
}
shouldComponentUpdate(nextProps, nextState) {
console.log('Should I update?');
// Change code below this line
return nextProps.value % 2 === 0;
// Change code above this line
}
componentDidUpdate() {
console.log('Component re-rendered.');
}
render() {
return <h1>{this.props.value}</h1>;
}
}
class Controller extends React.Component {
constructor(props) {
super(props);
this.state = {
value: 0
};
this.addValue = this.addValue.bind(this);
}
addValue() {
this.setState(state => ({
value: state.value + 1
}));
}
render() {
return (
<div>
<button onClick={this.addValue}>Add</button>
<OnlyEvens value={this.state.value} />
</div>
);
}
}