156 lines
4.0 KiB
Markdown
156 lines
4.0 KiB
Markdown
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---
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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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forumTopicId: 301410
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dashedName: render-with-an-if-else-condition
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---
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# --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 `if/else` statement in the `render()` method of a React component.
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# --instructions--
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MyComponent contains a `boolean` in its state which tracks whether you want to display some element in the UI or not. The `button` toggles the state of this value. Currently, it renders the same UI every time. Rewrite the `render()` method with an `if/else` statement so that if `display` is `true`, you return the current markup. Otherwise, return the markup without the `h1` element.
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**Note:** You must write an `if/else` to pass the tests. Use of the ternary operator will not pass here.
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# --hints--
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`MyComponent` should exist and render.
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```js
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assert(
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(function () {
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const mockedComponent = Enzyme.mount(React.createElement(MyComponent));
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return mockedComponent.find('MyComponent').length === 1;
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})()
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);
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```
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When `display` is set to `true`, a `div`, `button`, and `h1` should render.
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```js
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async () => {
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const waitForIt = (fn) =>
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new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250));
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const mockedComponent = Enzyme.mount(React.createElement(MyComponent));
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const state_1 = () => {
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mockedComponent.setState({ display: true });
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return waitForIt(() => mockedComponent);
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};
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const updated = await state_1();
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assert(
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mockedComponent.find('div').length === 1 &&
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mockedComponent.find('div').children().length === 2 &&
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mockedComponent.find('button').length === 1 &&
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mockedComponent.find('h1').length === 1
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);
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};
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```
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When `display` is set to `false`, only a `div` and `button` should render.
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```js
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async () => {
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const waitForIt = (fn) =>
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new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250));
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const mockedComponent = Enzyme.mount(React.createElement(MyComponent));
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const state_1 = () => {
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mockedComponent.setState({ display: false });
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return waitForIt(() => mockedComponent);
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};
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const updated = await state_1();
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assert(
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mockedComponent.find('div').length === 1 &&
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mockedComponent.find('div').children().length === 1 &&
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mockedComponent.find('button').length === 1 &&
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mockedComponent.find('h1').length === 0
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);
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};
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```
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The render method should use an `if/else` statement to check the condition of `this.state.display`.
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```js
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(getUserInput) =>
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assert(
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getUserInput('index').includes('if') &&
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getUserInput('index').includes('else')
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);
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```
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# --seed--
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## --after-user-code--
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```jsx
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ReactDOM.render(<MyComponent />, document.getElementById('root'))
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```
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## --seed-contents--
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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((state) => ({
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display: !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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# --solutions--
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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((state) => ({
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display: !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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