261 lines
7.7 KiB
Markdown
261 lines
7.7 KiB
Markdown
---
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id: 5a24c314108439a4d4036142
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title: Gerenciar state localmente primeiro
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challengeType: 6
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forumTopicId: 301431
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dashedName: manage-state-locally-first
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---
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# --description--
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Aqui você terminará de criar o componente `DisplayMessages`.
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# --instructions--
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Primeiro, no método `render()`, faça o componente renderizar os elementos `input`, `button` e `ul`. Quando o elemento `input` alterar, ele deve acionar o método `handleChange()`. Além disso, o elemento `input` deve renderizar o valor do `input` que está no state do componente. O elemento `button` deve acionar o método `submitMessage()` quando for clicado.
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Em segundo lugar, escreva esses dois métodos. O método `handleChange()` deve atualizar o `input` com o que o usuário digitar. O método `submitMessage()` deve concatenar a mensagem atual (armazenada em `input`) para o array `messages` no state local, e limpar o valor do `input`.
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Finalmente, use o `ul` para mapear em cima do array `messages` e o renderize na tela como uma lista de elementos `li`.
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# --hints--
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O componente `DisplayMessages` deve inicializar com o estado igual a `{ input: "", messages: [] }`.
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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(DisplayMessages));
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const initialState = mockedComponent.state();
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return (
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typeof initialState === 'object' &&
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initialState.input === '' &&
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initialState.messages.length === 0
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);
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})()
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);
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```
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O componente `DisplayMessages` deve renderizar um `div` contendo um elemento `h2`, um elemento `button`, um elemento `ul` e elementos `li` como filhos.
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```js
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async () => {
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const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages));
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const waitForIt = (fn) =>
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new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 100));
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const state = () => {
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mockedComponent.setState({ messages: ['__TEST__MESSAGE'] });
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return waitForIt(() => mockedComponent);
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};
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const updated = await state();
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assert(
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updated.find('div').length === 1 &&
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updated.find('h2').length === 1 &&
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updated.find('button').length === 1 &&
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updated.find('ul').length === 1 &&
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updated.find('li').length > 0
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);
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};
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```
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`.map` deve ser usado no array de `messages`.
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```js
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assert(code.match(/this\.state\.messages\.map/g));
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```
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O elemento `input` deve renderizar o valor de `input` no state local.
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```js
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async () => {
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const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages));
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const waitForIt = (fn) =>
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new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 100));
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const causeChange = (c, v) =>
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c.find('input').simulate('change', { target: { value: v } });
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const testValue = '__TEST__EVENT__INPUT';
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const changed = () => {
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causeChange(mockedComponent, testValue);
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return waitForIt(() => mockedComponent);
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};
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const updated = await changed();
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assert(updated.find('input').props().value === testValue);
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};
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```
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Chamar o método `handleChange` deve atualizar o valor do `input` no state para o input atual.
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```js
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async () => {
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const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages));
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const waitForIt = (fn) =>
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new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 100));
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const causeChange = (c, v) =>
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c.find('input').simulate('change', { target: { value: v } });
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const initialState = mockedComponent.state();
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const testMessage = '__TEST__EVENT__MESSAGE__';
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const changed = () => {
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causeChange(mockedComponent, testMessage);
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return waitForIt(() => mockedComponent);
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};
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const afterInput = await changed();
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assert(
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initialState.input === '' &&
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afterInput.state().input === '__TEST__EVENT__MESSAGE__'
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);
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};
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```
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Clicar o botão `Add message` deve chamar o método `submitMessage` o qual deve adicionar o texto atual no `input` ao array `messages` no state.
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```js
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async () => {
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const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages));
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const waitForIt = (fn) =>
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new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 100));
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const causeChange = (c, v) =>
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c.find('input').simulate('change', { target: { value: v } });
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const initialState = mockedComponent.state();
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const testMessage_1 = '__FIRST__MESSAGE__';
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const firstChange = () => {
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causeChange(mockedComponent, testMessage_1);
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return waitForIt(() => mockedComponent);
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};
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const firstResult = await firstChange();
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const firstSubmit = () => {
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mockedComponent.find('button').simulate('click');
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return waitForIt(() => mockedComponent);
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};
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const afterSubmit_1 = await firstSubmit();
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const submitState_1 = afterSubmit_1.state();
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const testMessage_2 = '__SECOND__MESSAGE__';
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const secondChange = () => {
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causeChange(mockedComponent, testMessage_2);
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return waitForIt(() => mockedComponent);
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};
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const secondResult = await secondChange();
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const secondSubmit = () => {
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mockedComponent.find('button').simulate('click');
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return waitForIt(() => mockedComponent);
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};
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const afterSubmit_2 = await secondSubmit();
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const submitState_2 = afterSubmit_2.state();
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assert(
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initialState.messages.length === 0 &&
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submitState_1.messages.length === 1 &&
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submitState_2.messages.length === 2 &&
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submitState_2.messages[1] === testMessage_2
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);
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};
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```
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O método `submitMessage` deve limpar o input atual.
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```js
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async () => {
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const mockedComponent = Enzyme.mount(React.createElement(DisplayMessages));
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const waitForIt = (fn) =>
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new Promise((resolve, reject) => setTimeout(() => resolve(fn()), 100));
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const causeChange = (c, v) =>
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c.find('input').simulate('change', { target: { value: v } });
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const initialState = mockedComponent.state();
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const testMessage = '__FIRST__MESSAGE__';
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const firstChange = () => {
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causeChange(mockedComponent, testMessage);
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return waitForIt(() => mockedComponent);
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};
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const firstResult = await firstChange();
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const firstState = firstResult.state();
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const firstSubmit = () => {
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mockedComponent.find('button').simulate('click');
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return waitForIt(() => mockedComponent);
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};
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const afterSubmit = await firstSubmit();
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const submitState = afterSubmit.state();
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assert(firstState.input === testMessage && submitState.input === '');
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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(<DisplayMessages />, document.getElementById('root'))
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```
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## --seed-contents--
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```jsx
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class DisplayMessages 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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messages: []
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}
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}
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// Add handleChange() and submitMessage() methods here
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render() {
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return (
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<div>
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<h2>Type in a new Message:</h2>
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{ /* Render an input, button, and ul 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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# --solutions--
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```jsx
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class DisplayMessages 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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messages: []
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}
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this.handleChange = this.handleChange.bind(this);
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this.submitMessage = this.submitMessage.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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submitMessage() {
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this.setState((state) => {
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const currentMessage = state.input;
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return {
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input: '',
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messages: state.messages.concat(currentMessage)
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};
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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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<h2>Type in a new Message:</h2>
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<input
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value={this.state.input}
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onChange={this.handleChange}/><br/>
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<button onClick={this.submitMessage}>Submit</button>
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<ul>
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{this.state.messages.map( (message, idx) => {
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return (
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<li key={idx}>{message}</li>
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)
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})
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}
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</ul>
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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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