// 建立元件
        class Login extends React.Component{
            state = {
                username: '',
                password: 
 
''
            }
            // 這就是函式的柯里化，接收了兩個引數：dataType、event
            saveFormData = (dataType) => {
                return (event) => {
                    this.setState({[dataType]: event.target.value})
                }
            }
            handleSubmit = (event) => {
                event.preventDefault() 
 
// 阻止表單提交
                const {username, password} = this.state
                alert(`使用者名稱是${username}，密碼是${password}`)
            }
            render() {
                return (
                    <form onSubmit={this.handleSubmit}>
                        使用者名稱：<input type="text" onChange={this
 
.saveFormData('username')} name="username"/>
                        密碼：<input type="password" onChange={this.saveFormData('password')} name="password"/>
                        <button>登入</button>
                    </form>
                )
            }
        }
        ReactDOM.render(<Login/>, document.getElementById('test'))