61 lines
2.2 KiB
Markdown
61 lines
2.2 KiB
Markdown
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---
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title: Use && for a More Concise Conditional
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localeTitle: 使用&&获得更简洁的条件
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---
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## 使用&&获得更简洁的条件
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给出的例子是
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```
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{condition && <p>markup</p>}
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```
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下面使用this.state.dinnerCooked布尔值的条件演示。 如果布尔值为true，则显示带有条件的{}中包含的标记，否则将不显示
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```
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class MyComponent 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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dinnerCooked: true
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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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{this.state.dinnerCooked &&<h1>Dinner is Cooked!</h1>}//h1 tag contents will be displayed
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</div>
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);
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}
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};
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## Hint:
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You don't have to do a full ```if/then``` statement. Just write the condition you are checking.
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## Solution:
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As you can see, you don't have to write the full ```if/then``` statement. We only need to check the condition and see if it returns ```true``` or ```false```. In this case, we are checking the value of ```display```. If the value is ```true```, then you return the value to the right of ```&&```, which is ```<h1>Displayed!</h1>```. If the condition is ```false```, it returns nothing.
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```
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JSX class MyComponent扩展了React.Component { 构造函数（道具）{ 超级（道具）; this.state = { 晚餐结束：假 }
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} render（）{
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回来（
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{this.state.dinnerCooked &&
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# 晚餐很熟！
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} // h1标签内容将不会显示 显示：true } this.toggleDisplay = this.toggleDisplay.bind（this）; } toggleDisplay（）{ this.setState（{ display：！this.state.display }）; } render（）{ //更改此行下方的代码 回来（
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切换显示 {this.state.display &&
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# 显示出来！
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}
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）; } }; \`\`\` 来自[ReactJS.org文档的说明](https://reactjs.org/docs/conditional-rendering.html)
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您可以通过将它们包装在花括号中来在JSX中嵌入任何表达式。这包括JavaScript逻辑&&运算符。它有条件地包括元素可以很方便
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它的工作原理是因为在JavaScript中，true &&表达式总是求值为表达式，而false &&表达式总是求值为false。
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因此，如果条件为真，则&&之后的元素将出现在输出中。如果是false，React将忽略并跳过它。
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