142 lines
7.4 KiB
Markdown
142 lines
7.4 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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console.info('after the test');
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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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