Manage State Locally First
Hints
Hint 1
Bind the method calls in component attributes with this
, e.g.
<input onChange={this.handleChange.bind(this)} value={this.state.input}/>
or the binding can be done beforehand
Hint 2
Pass event
to handleChange()
method declaration and note that event.target.value
stores the input value.
Hint 3
You may wanna add the following <div>
into render content to check if the handleChange()
method is working.
<div>{this.state.input}</div>
Hint 4
spread operator ...
can be used for array concatenation in submitMessage()
method declaration.
Solutions
Solution 1 (Click to Show/Hide)
class DisplayMessages extends React.Component {
constructor(props) {
super(props);
this.state = {
input: '',
messages: []
}
}
// add handleChange() and submitMessage() methods here
handleChange(event){
this.setState({
input: event.target.value,
messages: this.state.messages
})
}
submitMessage(){
this.setState({
input: '',
messages: [...this.state.messages, this.state.input]
})
}
render() {
return (
<div>
<h2>Type in a new Message:</h2>
{ /* render an input, button, and ul here */ }
<input onChange={this.handleChange.bind(this)} value={this.state.input}/>
<button onClick={this.submitMessage.bind(this)}>Submit</button>
<ul>
{this.state.messages.map((x, i)=>{
return <li key={i}>{x}</li>
})}
</ul>
{ /* change code above this line */ }
</div>
);
}
};