显示或隐藏React中的元素

我第一次摆弄React.js，找不到一种方法通过单击事件在页面上显示或隐藏一些东西。我没有加载任何其他库到页面，所以我正在寻找一些使用React库的本地方式。这是我目前得到的。我想在点击事件触发时显示结果div。

var Search= React.createClass({
    handleClick: function (event) {
        console.log(this.prop);
    },
    render: function () {
        return (
            <div className="date-range">
                <input type="submit" value="Search" onClick={this.handleClick} />
            </div>
        );
    }
});

var Results = React.createClass({
    render: function () {
        return (
            <div id="results" className="search-results">
                Some Results
            </div>
        );
    }
});

React.renderComponent(<Search /> , document.body);

当前回答

以下是我的方法。

import React, { useState } from 'react';

function ToggleBox({ title, children }) {
  const [isOpened, setIsOpened] = useState(false);

  function toggle() {
    setIsOpened(wasOpened => !wasOpened);
  }

  return (
    <div className="box">
      <div className="boxTitle" onClick={toggle}>
        {title}
      </div>
      {isOpened && (
        <div className="boxContent">
          {children}
        </div>
      )}
    </div>
  );
}

在上面的代码中，为了实现这一点，我使用了如下代码:

{opened && <SomeElement />}

仅当opened为true时才会呈现SomeElement。它的工作原理在于JavaScript解析逻辑条件的方式:

true && true && 2; // will output 2
true && false && 2; // will output false
true && 'some string'; // will output 'some string'
opened && <SomeElement />; // will output SomeElement if `opened` is true, will output false otherwise (and false will be ignored by react during rendering)
// be careful with 'falsy' values eg
const someValue = [];
someValue.length && <SomeElement /> // will output 0, which will be rednered by react
// it'll be better to:
someValue.length > 0 && <SomeElement /> // will render nothing as we cast the value to boolean

使用这种方法而不是CSS“display: none”的原因;

While it might be 'cheaper' to hide an element with CSS - in such case 'hidden' element is still 'alive' in react world (which might make it actually way more expensive) it means that if props of the parent element (eg. <TabView>) will change - even if you see only one tab, all 5 tabs will get re-rendered the hidden element might still have some lifecycle methods running - eg. it might fetch some data from the server after every update even tho it's not visible the hidden element might crash the app if it'll receive incorrect data. It might happen as you can 'forget' about invisible nodes when updating the state you might by mistake set wrong 'display' style when making element visible - eg. some div is 'display: flex' by default, but you'll set 'display: block' by mistake with display: invisible ? 'block' : 'none' which might break the layout using someBoolean && <SomeNode /> is very simple to understand and reason about, especially if your logic related to displaying something or not gets complex in many cases, you want to 'reset' element state when it re-appears. eg. you might have a slider that you want to set to initial position every time it's shown. (if that's desired behavior to keep previous element state, even if it's hidden, which IMO is rare - I'd indeed consider using CSS if remembering this state in a different way would be complicated)

2017-02-13 14:08:32

其他回答

下面是三元操作符的另一种语法:

{ this.state.showMyComponent ? <MyComponent /> : null }

等价于:

{ this.state.showMyComponent && <MyComponent /> }

学习的原因

还有显示的替代语法:'none';

<MyComponent style={this.state.showMyComponent ? {} : { display: 'none' }} />

然而，如果你过度使用display: 'none'，这将导致DOM污染，并最终降低应用程序的速度。

2016-09-08 22:52:35

在某些情况下，高阶分量可能有用:

创建高阶组件:

export var HidableComponent = (ComposedComponent) => class extends React.Component {
    render() {
        if ((this.props.shouldHide!=null && this.props.shouldHide()) || this.props.hidden)
            return null;
        return <ComposedComponent {...this.props}  />;
    }
};

扩展你自己的组件:

export const MyComp= HidableComponent(MyCompBasic);

然后你可以这样使用它:

<MyComp hidden={true} ... />
<MyComp shouldHide={this.props.useSomeFunctionHere} ... />

这减少了一点样板文件，并强制坚持命名约定，但请注意，MyComp仍然会被实例化-省略的方法是前面提到的:

{ ！hidden &&; <MyComp ... /> }

2016-11-13 08:57:45

以下是我的方法。

import React, { useState } from 'react';

function ToggleBox({ title, children }) {
  const [isOpened, setIsOpened] = useState(false);

  function toggle() {
    setIsOpened(wasOpened => !wasOpened);
  }

  return (
    <div className="box">
      <div className="boxTitle" onClick={toggle}>
        {title}
      </div>
      {isOpened && (
        <div className="boxContent">
          {children}
        </div>
      )}
    </div>
  );
}

在上面的代码中，为了实现这一点，我使用了如下代码:

{opened && <SomeElement />}

仅当opened为true时才会呈现SomeElement。它的工作原理在于JavaScript解析逻辑条件的方式:

true && true && 2; // will output 2
true && false && 2; // will output false
true && 'some string'; // will output 'some string'
opened && <SomeElement />; // will output SomeElement if `opened` is true, will output false otherwise (and false will be ignored by react during rendering)
// be careful with 'falsy' values eg
const someValue = [];
someValue.length && <SomeElement /> // will output 0, which will be rednered by react
// it'll be better to:
someValue.length > 0 && <SomeElement /> // will render nothing as we cast the value to boolean

使用这种方法而不是CSS“display: none”的原因;

2017-02-13 14:08:32

这个例子展示了如何通过使用每1秒切换一次的toggle来在组件之间切换

import React ,{Fragment,Component} from "react";
import ReactDOM from "react-dom";

import "./styles.css";

const Component1 = () =>(
  <div>
    <img 
src="https://i.pinimg.com/originals/58/df/1d/58df1d8bf372ade04781b8d4b2549ee6.jpg" />
   </div>
)

const Component2 = () => {
  return (
    <div>
       <img 
src="http://www.chinabuddhismencyclopedia.com/en/images/thumb/2/2e/12ccse.jpg/250px- 
12ccse.jpg" />
  </div>
   )

 }

 class App extends Component {
   constructor(props) {
     super(props);
    this.state = { 
      toggleFlag:false
     }
   }
   timer=()=> {
    this.setState({toggleFlag:!this.state.toggleFlag})
  }
  componentDidMount() {
    setInterval(this.timer, 1000);
   }
  render(){
     let { toggleFlag} = this.state
    return (
      <Fragment>
        {toggleFlag ? <Component1 /> : <Component2 />}
       </Fragment>
    )
  }
}


const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);

2019-02-09 18:19:20

我能够使用css属性“隐藏”。不知道可能的缺点。

export default function App() {
    const [hidden, setHidden] = useState(false);
    return (
      <div>
        <button onClick={() => setHidden(!hidden)}>HIDE</button>
        <div hidden={hidden}>hidden component</div>
      </div>
    );
  }

2020-11-29 08:41:59

显示或隐藏React中的元素

推荐文章

最新文章

标签