122 lines
4.8 KiB
Markdown
122 lines
4.8 KiB
Markdown
---
|
|
id: 5a24c314108439a4d4036184
|
|
title: Render with an If-Else Condition
|
|
challengeType: 6
|
|
isRequired: false
|
|
---
|
|
|
|
## Description
|
|
<section id='description'>
|
|
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.
|
|
</section>
|
|
|
|
## Instructions
|
|
<section id='instructions'>
|
|
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.
|
|
<strong>Note:</strong> You must write an <code>if/else</code> to pass the tests. Use of the ternary operator will not pass here.
|
|
</section>
|
|
|
|
## Tests
|
|
<section id='tests'>
|
|
|
|
```yml
|
|
tests:
|
|
- text: <code>MyComponent</code> should exist and render.
|
|
testString: assert((function() { const mockedComponent = Enzyme.mount(React.createElement(MyComponent)); return mockedComponent.find('MyComponent').length === 1; })(), '<code>MyComponent</code> should exist and render.');
|
|
- text: When <code>display</code> is set to <code>true</code>, a <code>div</code>, <code>button</code>, and <code>h1</code> should render.
|
|
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, ''When <code>display</code> is set to <code>true</code>, a <code>div</code>, <code>button</code>, and <code>h1</code> should render.''); }; '
|
|
- text: When <code>display</code> is set to <code>false</code>, only a <code>div</code> and <code>button</code> should render.
|
|
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, ''When <code>display</code> is set to <code>false</code>, only a <code>div</code> and <code>button</code> should render.''); }; '
|
|
- text: The render method should use an <code>if/else</code> statement to check the condition of <code>this.state.display</code>.
|
|
testString: getUserInput => assert(getUserInput('index').includes('if') && getUserInput('index').includes('else'), 'The render method should use an <code>if/else</code> statement to check the condition of <code>this.state.display</code>.');
|
|
|
|
```
|
|
|
|
</section>
|
|
|
|
## Challenge Seed
|
|
<section id='challengeSeed'>
|
|
|
|
<div id='jsx-seed'>
|
|
|
|
```jsx
|
|
class MyComponent extends React.Component {
|
|
constructor(props) {
|
|
super(props);
|
|
this.state = {
|
|
display: true
|
|
}
|
|
this.toggleDisplay = this.toggleDisplay.bind(this);
|
|
}
|
|
toggleDisplay() {
|
|
this.setState({
|
|
display: !this.state.display
|
|
});
|
|
}
|
|
render() {
|
|
// change code below this line
|
|
|
|
return (
|
|
<div>
|
|
<button onClick={this.toggleDisplay}>Toggle Display</button>
|
|
<h1>Displayed!</h1>
|
|
</div>
|
|
);
|
|
}
|
|
};
|
|
```
|
|
|
|
</div>
|
|
|
|
|
|
### After Test
|
|
<div id='jsx-teardown'>
|
|
|
|
```js
|
|
ReactDOM.render(<MyComponent />, document.getElementById('root'))
|
|
```
|
|
|
|
</div>
|
|
|
|
</section>
|
|
|
|
## Solution
|
|
<section id='solution'>
|
|
|
|
|
|
```js
|
|
class MyComponent extends React.Component {
|
|
constructor(props) {
|
|
super(props);
|
|
this.state = {
|
|
display: true
|
|
}
|
|
this.toggleDisplay = this.toggleDisplay.bind(this);
|
|
}
|
|
toggleDisplay() {
|
|
this.setState({
|
|
display: !this.state.display
|
|
});
|
|
}
|
|
render() {
|
|
// change code below this line
|
|
if (this.state.display) {
|
|
return (
|
|
<div>
|
|
<button onClick={this.toggleDisplay}>Toggle Display</button>
|
|
<h1>Displayed!</h1>
|
|
</div>
|
|
);
|
|
} else {
|
|
return (
|
|
<div>
|
|
<button onClick={this.toggleDisplay}>Toggle Display</button>
|
|
</div>
|
|
);
|
|
}
|
|
}
|
|
};
|
|
```
|
|
|
|
</section>
|