142 lines
7.5 KiB
Markdown
142 lines
7.5 KiB
Markdown
---
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id: 5a24c314108439a4d4036179
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title: Create a Controlled Form
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challengeType: 6
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isRequired: false
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---
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## Description
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<section id='description'>
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The last challenge showed that React can control the internal state for certain elements like <code>input</code> and <code>textarea</code>, which makes them controlled components. This applies to other form elements as well, including the regular HTML <code>form</code> element.
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</section>
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## Instructions
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<section id='instructions'>
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The <code>MyForm</code> component is set up with an empty <code>form</code> with a submit handler. The submit handler will be called when the form is submitted.
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We've added a button which submits the form. You can see it has the <code>type</code> set to <code>submit</code> indicating it is the button controlling the form. Add the <code>input</code> element in the <code>form</code> and set its <code>value</code> and <code>onChange()</code> attributes like the last challenge. You should then complete the <code>handleSubmit</code> method so that it sets the component state property <code>submit</code> to the current input value in the local <code>state</code>.
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<strong>Note:</strong> You also must call <code>event.preventDefault()</code> in the submit handler, to prevent the default form submit behavior which will refresh the web page.
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Finally, create an <code>h1</code> tag after the <code>form</code> which renders the <code>submit</code> value from the component's <code>state</code>. You can then type in the form and click the button (or press enter), and you should see your input rendered to the page.
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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>MyForm</code> should return a <code>div</code> element which contains a <code>form</code> and an <code>h1</code> tag. The form should include an <code>input</code> and a <code>button</code>.
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testString: assert((() => { const mockedComponent = Enzyme.mount(React.createElement(MyForm)); return (mockedComponent.find('div').children().find('form').length === 1 && mockedComponent.find('div').children().find('h1').length === 1 && mockedComponent.find('form').children().find('input').length === 1 && mockedComponent.find('form').children().find('button').length === 1) })(), '<code>MyForm</code> should return a <code>div</code> element which contains a <code>form</code> and an <code>h1</code> tag. The form should include an <code>input</code> and a <code>button</code>.');
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- text: The state of <code>MyForm</code> should initialize with <code>input</code> and <code>submit</code> properties, both set to empty strings.
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testString: assert(Enzyme.mount(React.createElement(MyForm)).state('input') === '' && Enzyme.mount(React.createElement(MyForm)).state('submit') === '', 'The state of <code>MyForm</code> should initialize with <code>input</code> and <code>submit</code> properties, both set to empty strings.');
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- text: Typing in the <code>input</code> element should update the <code>input</code> property of the component's state.
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testString: 'async () => { const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250)); const mockedComponent = Enzyme.mount(React.createElement(MyForm)); const _1 = () => { mockedComponent.setState({ input: '''' }); return waitForIt(() => mockedComponent.state(''input''))}; const _2 = () => { mockedComponent.find(''input'').simulate(''change'', { target: { value: ''TestInput'' }}); return waitForIt(() => ({ state: mockedComponent.state(''input''), inputVal: mockedComponent.find(''input'').props().value }))}; const before = await _1(); const after = await _2(); assert(before === '''' && after.state === ''TestInput'' && after.inputVal === ''TestInput'', ''Typing in the <code>input</code> element should update the <code>input</code> property of the component's state.''); }; '
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- text: Submitting the form should run <code>handleSubmit</code> which should set the <code>submit</code> property in state equal to the current input.
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testString: 'async () => { const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250)); const mockedComponent = Enzyme.mount(React.createElement(MyForm)); const _1 = () => { mockedComponent.setState({ input: '''' }); mockedComponent.setState({submit: ''''}); mockedComponent.find(''input'').simulate(''change'', {target: {value: ''SubmitInput''}}); return waitForIt(() => mockedComponent.state(''submit''))}; const _2 = () => { mockedComponent.find(''form'').simulate(''submit''); return waitForIt(() => mockedComponent.state(''submit''))}; const before = await _1(); const after = await _2(); assert(before === '''' && after === ''SubmitInput'', ''Submitting the form should run <code>handleSubmit</code> which should set the <code>submit</code> property in state equal to the current input.''); };'
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- text: The <code>h1</code> header should render the value of the <code>submit</code> field from the component's state.
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testString: 'async () => { const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 250)); const mockedComponent = Enzyme.mount(React.createElement(MyForm)); const _1 = () => { mockedComponent.setState({ input: '''' }); mockedComponent.setState({submit: ''''}); mockedComponent.find(''input'').simulate(''change'', {target: {value: ''TestInput''}}); return waitForIt(() => mockedComponent.find(''h1'').text())}; const _2 = () => { mockedComponent.find(''form'').simulate(''submit''); return waitForIt(() => mockedComponent.find(''h1'').text())}; const before = await _1(); const after = await _2(); assert(before === '''' && after === ''TestInput'', ''The <code>h1</code> header should render the value of the <code>submit</code> field from the component's state.''); }; '
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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 MyForm 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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input: '',
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submit: ''
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};
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this.handleChange = this.handleChange.bind(this);
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this.handleSubmit = this.handleSubmit.bind(this);
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}
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handleChange(event) {
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this.setState({
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input: event.target.value
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});
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}
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handleSubmit(event) {
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// change code below this line
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// change code above this line
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}
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render() {
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return (
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<div>
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<form onSubmit={this.handleSubmit}>
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{ /* change code below this line */ }
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{ /* change code above this line */ }
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<button type='submit'>Submit!</button>
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</form>
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{ /* change code below this line */ }
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{ /* change code above this line */ }
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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(<MyForm />, 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 MyForm 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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input: '',
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submit: ''
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};
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this.handleChange = this.handleChange.bind(this);
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this.handleSubmit = this.handleSubmit.bind(this);
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}
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handleChange(event) {
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this.setState({
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input: event.target.value
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});
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}
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handleSubmit(event) {
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event.preventDefault()
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this.setState({
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submit: this.state.input
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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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<form onSubmit={this.handleSubmit}>
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<input
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value={this.state.input}
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onChange={this.handleChange} />
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<button type='submit'>Submit!</button>
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</form>
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<h1>{this.state.submit}</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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</section>
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