4.0 KiB
4.0 KiB
id | title | challengeType | isRequired | videoUrl | localeTitle |
---|---|---|---|---|---|
5a24c314108439a4d4036176 | Use State to Toggle an Element | 6 | false | 使用State切换元素 |
Description
state
。一个示例是监视值的状态,然后根据此值有条件地呈现UI。有几种不同的方法可以实现这一点,代码编辑器显示了一种方法。 Instructions
MyComponent
有一个visibility
属性,初始化为false
。如果visibility
值为true,则render方法返回一个视图;如果为false,则返回不同的视图。目前,无法更新组件state
的visibility
属性。该值应在true和false之间来回切换。按钮上有一个单击处理程序,它触发一个名为toggleVisibility()
的类方法。定义此方法,以便在调用方法时, visibility
state
切换为相反的值。如果visibility
是false
,该方法将其设置为true
,反之亦然。最后,单击按钮以根据其state
查看组件的条件呈现。 提示:不要忘记将this
关键字绑定到构造函数中的方法! Tests
tests:
- text: <code>MyComponent</code>应该返回一个包含<code>button</code>的<code>div</code>元素。
testString: 'assert.strictEqual(Enzyme.mount(React.createElement(MyComponent)).find("div").find("button").length, 1, "<code>MyComponent</code> should return a <code>div</code> element which contains a <code>button</code>.");'
- text: <code>MyComponent</code>的状态应该初始化,并将<code>visibility</code>属性设置为<code>false</code> 。
testString: 'assert.strictEqual(Enzyme.mount(React.createElement(MyComponent)).state("visibility"), false, "The state of <code>MyComponent</code> should initialize with a <code>visibility</code> property set to <code>false</code>.");'
- text: 单击按钮元素应该在<code>true</code>和<code>false</code>之间切换状态的<code>visibility</code>属性。
testString: 'async () => { const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250)); const mockedComponent = Enzyme.mount(React.createElement(MyComponent)); const first = () => { mockedComponent.setState({ visibility: false }); return waitForIt(() => mockedComponent.state("visibility")); }; const second = () => { mockedComponent.find("button").simulate("click"); return waitForIt(() => mockedComponent.state("visibility")); }; const third = () => { mockedComponent.find("button").simulate("click"); return waitForIt(() => mockedComponent.state("visibility")); }; const firstValue = await first(); const secondValue = await second(); const thirdValue = await third(); assert(!firstValue && secondValue && !thirdValue, "Clicking the button element should toggle the <code>visibility</code> property in state between <code>true</code> and <code>false</code>."); }; '
Challenge Seed
class MyComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
visibility: false
};
// change code below this line
// change code above this line
}
// change code below this line
// change code above this line
render() {
if (this.state.visibility) {
return (
<div>
<button onClick={this.toggleVisibility}>Click Me</button>
<h1>Now you see me!</h1>
</div>
);
} else {
return (
<div>
<button onClick={this.toggleVisibility}>Click Me</button>
</div>
);
}
}
};
After Test
console.info('after the test');
Solution
// solution required