123 lines
4.4 KiB
Markdown
123 lines
4.4 KiB
Markdown
---
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id: 5a24c314108439a4d4036184
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title: Render with an If-Else Condition
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challengeType: 6
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isRequired: false
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forumTopicId: 301410
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---
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## Description
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<section id='description'>
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Another application of using JavaScript to control your rendered view is to tie the elements that are rendered to a condition. When the condition is true, one view renders. When it's false, it's a different view. You can do this with a standard <code>if/else</code> statement in the <code>render()</code> method of a React component.
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</section>
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## Instructions
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<section id='instructions'>
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MyComponent contains a <code>boolean</code> in its state which tracks whether you want to display some element in the UI or not. The <code>button</code> toggles the state of this value. Currently, it renders the same UI every time. Rewrite the <code>render()</code> method with an <code>if/else</code> statement so that if <code>display</code> is <code>true</code>, you return the current markup. Otherwise, return the markup without the <code>h1</code> element.
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<strong>Note:</strong> You must write an <code>if/else</code> to pass the tests. Use of the ternary operator will not pass here.
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>MyComponent</code> should exist and render.
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testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(MyComponent)); return mockedComponent.find('MyComponent').length === 1; })());
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- text: When <code>display</code> is set to <code>true</code>, a <code>div</code>, <code>button</code>, and <code>h1</code> should render.
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testString: 'async () => { const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250)); const mockedComponent = Enzyme.mount(React.createElement(MyComponent)); const state_1 = () => { mockedComponent.setState({display: true}); return waitForIt(() => mockedComponent )}; const updated = await state_1(); assert(mockedComponent.find(''div'').length === 1 && mockedComponent.find(''div'').children().length === 2 && mockedComponent.find(''button'').length === 1 && mockedComponent.find(''h1'').length === 1); }; '
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- text: When <code>display</code> is set to <code>false</code>, only a <code>div</code> and <code>button</code> should render.
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testString: 'async () => { const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250)); const mockedComponent = Enzyme.mount(React.createElement(MyComponent)); const state_1 = () => { mockedComponent.setState({display: false}); return waitForIt(() => mockedComponent )}; const updated = await state_1(); assert(mockedComponent.find(''div'').length === 1 && mockedComponent.find(''div'').children().length === 1 && mockedComponent.find(''button'').length === 1 && mockedComponent.find(''h1'').length === 0); }; '
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- text: The render method should use an <code>if/else</code> statement to check the condition of <code>this.state.display</code>.
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testString: getUserInput => assert(getUserInput('index').includes('if') && getUserInput('index').includes('else'));
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='jsx-seed'>
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```jsx
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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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display: true
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}
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this.toggleDisplay = this.toggleDisplay.bind(this);
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}
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toggleDisplay() {
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this.setState({
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display: !this.state.display
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});
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}
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render() {
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// change code below this line
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return (
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<div>
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<button onClick={this.toggleDisplay}>Toggle Display</button>
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<h1>Displayed!</h1>
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</div>
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);
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}
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};
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```
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</div>
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### After Test
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<div id='jsx-teardown'>
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```js
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ReactDOM.render(<MyComponent />, document.getElementById('root'))
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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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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display: true
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}
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this.toggleDisplay = this.toggleDisplay.bind(this);
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}
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toggleDisplay() {
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this.setState({
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display: !this.state.display
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});
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}
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render() {
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// change code below this line
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if (this.state.display) {
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return (
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<div>
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<button onClick={this.toggleDisplay}>Toggle Display</button>
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<h1>Displayed!</h1>
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</div>
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);
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} else {
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return (
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<div>
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<button onClick={this.toggleDisplay}>Toggle Display</button>
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</div>
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);
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}
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}
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};
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```
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</section>
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