75 lines
1.6 KiB
Markdown
75 lines
1.6 KiB
Markdown
---
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title: Use Array.map() to Dynamically Render Elements
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localeTitle: 使用Array.map（）动态渲染元素
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---
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## 使用Array.map（）动态渲染元素
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## 提示1：
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将两个状态定义为JavaScript `object` 。
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```javascript
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{object: state, object: state}
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```
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## 提示2：
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您需要`.map()`为数组中的每个对象生成一行。
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```javascript
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this.state.toDoList.map(i => <li>{i}</li>);
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```
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## 解：
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添加地图功能后，您会注意到它会为您放入列表中的每个项目生成`<li>` 。
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```jsx
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const textAreaStyles = {
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width: 235,
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margin: 5
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};
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class MyToDoList extends React.Component {
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constructor(props) {
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super(props);
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// change code below this line
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this.state = {
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userInput: '',
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toDoList: []
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}
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// change code above this line
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this.handleSubmit = this.handleSubmit.bind(this);
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this.handleChange = this.handleChange.bind(this);
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}
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handleSubmit() {
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const itemsArray = this.state.userInput.split(',');
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this.setState({
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toDoList: itemsArray
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});
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}
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handleChange(e) {
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this.setState({
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userInput: e.target.value
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});
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}
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render() {
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const items = this.state.toDoList.map(i => <li>{i}</li>); // change code here
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return (
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<div>
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<textarea
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onChange={this.handleChange}
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value={this.state.userInput}
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style={textAreaStyles}
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placeholder="Separate Items With Commas" /><br />
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<button onClick={this.handleSubmit}>Create List</button>
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<h1>My "To Do" List:</h1>
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<ul>
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{items}
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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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``` |