1494a50123
* fix: restructure certifications guide articles * fix: added 3 dashes line before prob expl * fix: added 3 dashes line before hints * fix: added 3 dashes line before solutions
78 lines
1.7 KiB
Markdown
78 lines
1.7 KiB
Markdown
---
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title: Manage State Locally First
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---
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# Manage State Locally First
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---
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## Hints
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### Hint 1
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Bind the method calls in component attributes with ```this```, e.g.
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```jsx
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<input onChange={this.handleChange.bind(this)} value={this.state.input}/>
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```
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or the binding can be done beforehand
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### Hint 2
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Pass ```event``` to ```handleChange()``` method declaration and note that ```event.target.value``` stores the input value.
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### Hint 3
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You may wanna add the following ```<div>``` into render content to check if the ```handleChange()``` method is working.
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```jsx
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<div>{this.state.input}</div>
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```
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### Hint 4
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spread operator ```...``` can be used for array concatenation in ```submitMessage()``` method declaration.
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---
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## Solutions
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<details><summary>Solution 1 (Click to Show/Hide)</summary>
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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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handleChange(event){
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this.setState({
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input: event.target.value,
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messages: this.state.messages
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})
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}
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submitMessage(){
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this.setState({
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input: '',
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messages: [...this.state.messages, 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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<h2>Type in a new Message:</h2>
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{ /* render an input, button, and ul here */ }
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<input onChange={this.handleChange.bind(this)} value={this.state.input}/>
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<button onClick={this.submitMessage.bind(this)}>Submit</button>
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<ul>
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{this.state.messages.map((x, i)=>{
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return <li key={i}>{x}</li>
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})}
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</ul>
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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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</details>
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