135 lines
8.7 KiB
Markdown
135 lines
8.7 KiB
Markdown
---
|
|
id: 5a24c314108439a4d4036142
|
|
title: Manage State Locally First
|
|
challengeType: 6
|
|
isRequired: false
|
|
---
|
|
|
|
## Description
|
|
<section id='description'>
|
|
Here you'll finish creating the <code>DisplayMessages</code> component.
|
|
</section>
|
|
|
|
## Instructions
|
|
<section id='instructions'>
|
|
First, in the <code>render()</code> method, have the component render an <code>input</code> element, <code>button</code> element, and <code>ul</code> element. When the <code>input</code> element changes, it should trigger a <code>handleChange()</code> method. Also, the <code>input</code> element should render the value of <code>input</code> that's in the component's state. The <code>button</code> element should trigger a <code>submitMessage()</code> method when it's clicked.
|
|
Second, write these two methods. The <code>handleChange()</code> method should update the <code>input</code> with what the user is typing. The <code>submitMessage()</code> method should concatenate the current message (stored in <code>input</code>) to the <code>messages</code> array in local state, and clear the value of the <code>input</code>.
|
|
Finally, use the <code>ul</code> to map over the array of <code>messages</code> and render it to the screen as a list of <code>li</code> elements.
|
|
</section>
|
|
|
|
## Tests
|
|
<section id='tests'>
|
|
|
|
```yml
|
|
tests:
|
|
- text: 'The <code>DisplayMessages</code> component should initialize with a state equal to <code>{ input: "", messages: [] }</code>.'
|
|
testString: 'assert((function() { const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages)); const initialState = mockedComponent.state(); return ( typeof initialState === ''object'' && initialState.input === '''' && initialState.messages.length === 0); })(), ''The <code>DisplayMessages</code> component should initialize with a state equal to <code>{ input: "", messages: [] }</code>.'');'
|
|
- text: 'The <code>DisplayMessages</code> component should render a <code>div</code> containing an <code>h2</code> element, a <code>button</code> element, a <code>ul</code> element, and <code>li</code> elements as children.'
|
|
testString: 'async () => { const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages)); const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 100)); const state = () => { mockedComponent.setState({messages: [''__TEST__MESSAGE'']}); return waitForIt(() => mockedComponent )}; const updated = await state(); assert(updated.find(''div'').length === 1 && updated.find(''h2'').length === 1 && updated.find(''button'').length === 1 && updated.find(''ul'').length === 1, ''The <code>DisplayMessages</code> component should render a <code>div</code> containing an <code>h2</code> element, a <code>button</code> element, a <code>ul</code> element, and <code>li</code> elements as children.''); }; '
|
|
- text: The <code>input</code> element should render the value of <code>input</code> in local state.
|
|
testString: 'async () => { const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages)); const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 100)); const causeChange = (c, v) => c.find(''input'').simulate(''change'', { target: { value: v }}); const testValue = ''__TEST__EVENT__INPUT''; const changed = () => { causeChange(mockedComponent, testValue); return waitForIt(() => mockedComponent )}; const updated = await changed(); assert(updated.find(''input'').props().value === testValue, ''The <code>input</code> element should render the value of <code>input</code> in local state.''); }; '
|
|
- text: Calling the method <code>handleChange</code> should update the <code>input</code> value in state to the current input.
|
|
testString: 'async () => { const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages)); const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 100)); const causeChange = (c, v) => c.find(''input'').simulate(''change'', { target: { value: v }}); const initialState = mockedComponent.state(); const testMessage = ''__TEST__EVENT__MESSAGE__''; const changed = () => { causeChange(mockedComponent, testMessage); return waitForIt(() => mockedComponent )}; const afterInput = await changed(); assert(initialState.input === '''' && afterInput.state().input === ''__TEST__EVENT__MESSAGE__'', ''Calling the method <code>handleChange</code> should update the <code>input</code> value in state to the current input.''); }; '
|
|
- text: Clicking the <code>Add message</code> button should call the method <code>submitMessage</code> which should add the current <code>input</code> to the <code>messages</code> array in state.
|
|
testString: 'async () => { const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages)); const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 100)); const causeChange = (c, v) => c.find(''input'').simulate(''change'', { target: { value: v }}); const initialState = mockedComponent.state(); const testMessage_1 = ''__FIRST__MESSAGE__''; const firstChange = () => { causeChange(mockedComponent, testMessage_1); return waitForIt(() => mockedComponent )}; const firstResult = await firstChange(); const firstSubmit = () => { mockedComponent.find(''button'').simulate(''click''); return waitForIt(() => mockedComponent )}; const afterSubmit_1 = await firstSubmit(); const submitState_1 = afterSubmit_1.state(); const testMessage_2 = ''__SECOND__MESSAGE__''; const secondChange = () => { causeChange(mockedComponent, testMessage_2); return waitForIt(() => mockedComponent )}; const secondResult = await secondChange(); const secondSubmit = () => { mockedComponent.find(''button'').simulate(''click''); return waitForIt(() => mockedComponent )}; const afterSubmit_2 = await secondSubmit(); const submitState_2 = afterSubmit_2.state(); assert(initialState.messages.length === 0 && submitState_1.messages.length === 1 && submitState_2.messages.length === 2 && submitState_2.messages[1] === testMessage_2, ''Clicking the <code>Add message</code> button should call the method <code>submitMessage</code> which should add the current <code>input</code> to the <code>messages</code> array in state.''); }; '
|
|
- text: The <code>submitMessage</code> method should clear the current input.
|
|
testString: 'async () => { const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages)); const waitForIt = (fn) => new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 100)); const causeChange = (c, v) => c.find(''input'').simulate(''change'', { target: { value: v }}); const initialState = mockedComponent.state(); const testMessage = ''__FIRST__MESSAGE__''; const firstChange = () => { causeChange(mockedComponent, testMessage); return waitForIt(() => mockedComponent )}; const firstResult = await firstChange(); const firstState = firstResult.state(); const firstSubmit = () => { mockedComponent.find(''button'').simulate(''click''); return waitForIt(() => mockedComponent )}; const afterSubmit = await firstSubmit(); const submitState = afterSubmit.state(); assert(firstState.input === testMessage && submitState.input === '''', ''The <code>submitMessage</code> method should clear the current input.''); }; '
|
|
|
|
```
|
|
|
|
</section>
|
|
|
|
## Challenge Seed
|
|
<section id='challengeSeed'>
|
|
|
|
<div id='jsx-seed'>
|
|
|
|
```jsx
|
|
class DisplayMessages extends React.Component {
|
|
constructor(props) {
|
|
super(props);
|
|
this.state = {
|
|
input: '',
|
|
messages: []
|
|
}
|
|
}
|
|
// add handleChange() and submitMessage() methods here
|
|
|
|
render() {
|
|
return (
|
|
<div>
|
|
<h2>Type in a new Message:</h2>
|
|
{ /* render an input, button, and ul here */ }
|
|
|
|
{ /* change code above this line */ }
|
|
</div>
|
|
);
|
|
}
|
|
};
|
|
```
|
|
|
|
</div>
|
|
|
|
|
|
### After Test
|
|
<div id='jsx-teardown'>
|
|
|
|
```js
|
|
console.info('after the test');
|
|
```
|
|
|
|
</div>
|
|
|
|
</section>
|
|
|
|
## Solution
|
|
<section id='solution'>
|
|
|
|
|
|
```js
|
|
class DisplayMessages extends React.Component {
|
|
constructor(props) {
|
|
super(props);
|
|
this.state = {
|
|
input: '',
|
|
messages: []
|
|
}
|
|
this.handleChange = this.handleChange.bind(this);
|
|
this.submitMessage = this.submitMessage.bind(this);
|
|
}
|
|
handleChange(event) {
|
|
this.setState({
|
|
input: event.target.value
|
|
});
|
|
}
|
|
submitMessage() {
|
|
const currentMessage = this.state.input;
|
|
this.setState({
|
|
input: '',
|
|
messages: this.state.messages.concat(currentMessage)
|
|
});
|
|
}
|
|
render() {
|
|
return (
|
|
<div>
|
|
<h2>Type in a new Message:</h2>
|
|
<input
|
|
value={this.state.input}
|
|
onChange={this.handleChange}/><br/>
|
|
<button onClick={this.submitMessage}>Submit</button>
|
|
<ul>
|
|
{this.state.messages.map( (message, idx) => {
|
|
return (
|
|
<li key={idx}>{message}</li>
|
|
)
|
|
})
|
|
}
|
|
</ul>
|
|
</div>
|
|
);
|
|
}
|
|
};
|
|
```
|
|
|
|
</section>
|