React的基本知识:事件监听器、Props和State的区分、改变state的方法、使用回调函数改变state、使用三元运算符改变state

发布于:2024-11-28 ⋅ 阅读:(39) ⋅ 点赞:(0)

这篇教学文章涵盖了大量的React基本知识。
包括:

  • 事件监听器
  • Props和State的区分
  • 改变state的方法
  • 使用回调函数改变state
  • 使用三元运算符改变state
  • 处理state中的数组
  • 处理state中的object
  • 条件渲染 &&
  • 条件渲染 三元运算符
  • React中的forms

1. Event Listeners

在React中,事件监听器(Event Listeners)是用于响应用户操作(如点击、输入、鼠标移动等)的函数。
React中的事件监听器通常以camelCase形式命名,而不是使用HTML中的小写命名。例如,HTML中的onclick在React中写作onClick。
在React组件中,你可以在JSX中直接添加事件监听器。这些监听器是作为组件的属性添加的,其值是一个函数,当事件触发时,这个函数会被调用。

export default function App(){
  function handleClick(){
    console.log("I was clicked!")
  }
  function handleOnMouseOver (){
    console.log("MouseOver")
  }

  return (
    <div>
      <img 
        src="https://picsum.photos/640/360"
        onMouseOver={handleOnMouseOver}
      />
      <button onClick={handleClick}>Click me</button>
    </div>
  )
}

2. Props vs. State

“Props” refers to the properties being passed into a component in order for it to work correctly, similar to how a function receives parameters. A component receiving props is not allowed to modify those props. (i.e. they are “immutable”)

“State” refers to values that are managed by the component, similar to variables declared inside a function. Anytime you have changing values that should be saved/displayed, you will likely be using state.

在React中,组件的数据管理主要通过两种属性来实现:props(属性)和state(状态)。理解它们之间的区别对于构建有效的React应用至关重要。
Props(属性)

  • 不可变性:Props是从父组件传递到子组件的数据,它们是不可变的。这意味着一旦props被传递给组件,组件就不能直接修改这些props的值。如果需要改变props的值,必须通过父组件来完成。
  • 单向数据流:Props支持React的单向数据流原则,即数据只能从父组件流向子组件,这有助于避免数据流的混乱和应用状态的不可预测性。

State(状态)

  • 可变性:State是组件内部管理的数据,它可以在组件的生命周期内被改变。State的变化会触发组件的重新渲染。
  • 组件内部管理:State是私有的,只能在声明它的组件内部被直接访问和修改。State的变化通常是由于用户交互或程序逻辑的需要。
  • 触发渲染:当组件的state发生变化时,React会重新渲染组件,以确保UI与最新的状态保持同步。

3. Changing State

在React中,“changing state”(改变状态)是指更新组件内部的状态(state)。状态是React组件的私有数据,它可以帮助组件记录和响应用户操作或其他事件。当状态发生变化时,React会重新渲染组件,以确保UI与最新的状态保持同步。

改变状态的方法
在类组件中,状态通过this.setState()方法更新,在函数组件中,状态通过useState钩子(hook)的设置函数(setter function)更新。

类组件中改变状态
在类组件中,状态是使用this.state来声明的,而this.setState()方法用来更新状态。

函数组件中改变状态
在函数组件中,useState钩子允许你添加状态到函数组件中。useState返回一个数组,其中包含当前状态值和一个可以更新该状态的函数。


import React from "react"

export default function App(){

  const [isImportant, setIsImportant] = React.useState("YES")
  function handleClick(){
    setIsImportant("NO")
  }
  return (
    <div>
      <h1>Is state important to know?</h1>
      <div onClick={handleClick}>
        <h1>{isImportant}</h1>
      </div>
    </div>
  )

  
}

4. Changing state with a callback function

在React中,使用回调函数(callback function)来改变状态是一种常见的做法,尤其是在你需要基于当前状态来更新状态时。这种模式允许你在状态更新时立即获取最新的状态值,这对于执行依赖于前一个状态的计算特别有用。


import React from "react"

export default function App(){
  const [count, setCount] = React.useState(0)

  function add(){
    setCount(prevCount => prevCount+1)
  }
  function subtract(){
    setCount(prevCount => prevCount-1)
  }

  return (
    <div>
      <button onClick={subtract}>-</button>
      <div>
        <h1>{count}</h1>
      </div>
      <button onClick={add}>+</button>
    </div>
  )

  
}

5. Changing state: ternary

在React中,使用三元运算符(ternary operator)来改变状态是一种简洁的方式来根据条件选择新的状态值。三元运算符是一种表达式,它有三个操作数:一个条件、一个真值和一个假值。如果条件为真,则返回真值;如果条件为假,则返回假值。

import React from "react"

export default function App(){

  const [isGoingOut, setIsGoingOut] = React.useState(true)

  function changeMind(){
    setIsGoingOut(prevState => !prevState)
  }

  return (
    <div>
      <h1>Do I feel like going out tonight?</h1>
      <div onClick={changeMind}>
        <h1>{isGoingOut ? "Yes" : "No"}</h1>
      </div>
    </div>
  )
}

6. Complex State: arrays

在React中处理复杂状态,尤其是涉及到数组时,我们需要特别小心,因为数组是引用类型直接修改数组不会触发组件的重新渲染。以下是一些关于如何在React中处理复杂状态,特别是数组的要点:

  1. 不要直接修改状态
    直接修改数组(如通过索引赋值或使用push、pop等方法)不会触发组件的重新渲染。这是因为React使用浅比较来检测状态的变化。因此,任何对数组的修改都应该通过创建一个新数组来完成,以确保状态的变化能够被React检测到。
  2. 使用函数式更新
    在函数组件中,当需要基于当前状态来更新数组时,应该使用函数式更新。这意味着传递一个函数给setState(或在useState中的设置函数),这个函数接收当前状态作为参数,并返回新的状态。
import React from "react"

export default function App(){

  const [thingsArray, setThingsArray] = React.useState(["Thing 1", "Thing 2"])

  function addItem(){
    setThingsArray(prevState => {
      return [...prevState, `Thing ${prevState.length + 1}`]
    })
  }

  const thingsElements = thingsArray.map(thing => <p key={thing}>{thing}</p>)

  return (
    <div>
      <button onClick={addItem}>Add Item</button>
      {thingsElements}
    </div>
  )

  
}

在这个例子中,我们通过扩展运算符…来创建一个新数组,包含旧数组的所有元素以及新添加的元素,这样可以确保状态的变化。

7. Complex state: objects

在React中处理复杂状态,尤其是涉及到对象时,与处理数组类似,需要特别注意不可变性(immutability)。这是因为React依赖于比较状态的新旧值来决定是否重新渲染组件。如果直接修改对象,React可能无法检测到状态的变化,从而不会触发组件的重新渲染。

  1. 不要直接修改状态
    直接修改对象(如添加、删除或修改对象的属性)不会触发组件的重新渲染。因此,任何对对象状态的修改都应该通过创建一个新对象来完成。
  2. 使用函数式更新
    在函数组件中,当需要基于当前状态来更新对象时,应该使用函数式更新。这意味着传递一个函数给setState(或在useState中的设置函数),这个函数接收当前状态作为参数,并返回新的状态。
import React from "react"

export default function App(){

  const [contact, setContact] = React.useState({
    firstName: "John",
    lastName: "Doe",
    phone: "+1 (719) 555-1212",
    email: "itsmyrealname@example.com",
    isFavorite: true
  })

  let starIcon = contact.isFavorite ? "star-filled.png" : "star-empty.png"

  function toggleFavorite(){
    console.log("Toggle Favorite")
  }

  return (
    <main>
      <article>
        <img src="images/user.png" />
        <div>
          <img
            src={`images/${starIcon}`}
            onClick={toggleFavorite}
          />
          <h2>
            {contact.firstName} {contact.lastName}
          </h2>
          <p>{contact.phone}</p>
          <p>{contact.email}</p>
        </div>
      </article>
    </main>
  )

  
}

在这里插入图片描述
star-empty.png
在这里插入图片描述
star-filled.png
在这里插入图片描述
user.png

8. Complex state: updating state object

在这个例子中,我们通过扩展运算符…来创建一个新对象,包含旧对象的所有属性以及新修改的属性,这样可以确保状态的变化能够被React检测到。

import React from "react"

export default function App(){

  const [contact, setContact] = React.useState({
    firstName: "John",
    lastName: "Doe",
    phone: "+1 (719) 555-1212",
    email: "itsmyrealname@example.com",
    isFavorite: true
  })

  let starIcon = contact.isFavorite ? "star-filled.png" : "star-empty.png"

  function toggleFavorite(){
    setContact(prevContact => ({
      ...prevContact,
      isFavorite: !prevContact.isFavorite
    }))
  }

  return (
    <main>
      <article>
        <img src="images/user.png" />
        <div>
          <img
            src={`images/${starIcon}`}
            onClick={toggleFavorite}
          />
          <h2>
            {contact.firstName} {contact.lastName}
          </h2>
          <p>{contact.phone}</p>
          <p>{contact.email}</p>
        </div>
      </article>
    </main>
  )

  
}

9. Flip the box

App.jsx

import React from "react"
import boxes from "../public/components/boxes";
import Box from "../public/components/Box";

export default function App(){

  const [squares, setSquares] = React.useState(boxes)

  const squareElements = squares.map(square => (
    <Box key={square.id} on={square.on} />
  ))

  return (
    <main>
      {squareElements}
    </main>
  )

  
}

boxes.jsx

export default [
    {
        id: 1,
        on: true
    },   
    {
        id: 2,
        on: false
    },   
    {
        id: 3,
        on: true
    },   
    {
        id: 4,
        on: true
    },   
    {
        id: 5,
        on: false
    },   
    {
        id: 6,
        on: false
    },   
]

Box.jsx

import React from "react"

export default function Box(props) {
    const [on, setOn] = React.useState(props.on)

    const styles = {
        backgroundColor: on ? "#222222" : "transparent"
    }

    function toggle(){
        setOn(prevOn => !prevOn)
    }

    return (
        <div 
            style={styles} 
            className="box"
            onClick={toggle}    
        ></div>
    )
}

index.css

* {
  box-sizing: border-box;
}

body {
  font-family: "Karla", sans-serif;
  margin: 0;
}

.box {
  height: 100px;
  width: 100px;
  border: 1px solid black;
  display: inline-block;
  margin-right: 4px;
  border-radius: 5px;
}

10. Flip the box (use ternary operator)

App.jsx

import React from "react"
import boxes from "../public/components/boxes";
import Box from "../public/components/Box";

export default function App(){

  const [squares, setSquares] = React.useState(boxes)

  function toggle(id) {
    setSquares(prevSquares => {
      return prevSquares.map((square) => {
        return square.id === id ? {...square, on: !square.on} : square
      })
    })
  }

  const squareElements = squares.map(square => (
    <Box 
      key={square.id}
      on={square.on}
      toggle={() => toggle(square.id)} />
  ))

  return (
    <main>
      {squareElements}
    </main>
  )

  
}

Box.jsx

import React from "react"

export default function Box(props) {

    const styles = {
        backgroundColor: props.on ? "#222222" : "transparent"
    }

    return (
        <div 
            style={styles} 
            className="box"
            onClick={props.toggle}    
        ></div>
    )
}

11. Conditional rendering: &&

在React中,条件渲染是指根据某些条件来决定是否渲染某些组件或元素。这可以通过多种方式实现,包括使用JavaScript的逻辑与(&&)操作符。逻辑与操作符&&在条件渲染中非常有用,因为它允许你在同一个表达式中进行条件检查和元素渲染。
使用&&进行条件渲染
当你使用&&操作符时,如果其左边的表达式为真(truthy),则整个表达式的结果将取决于右边的表达式。在JSX中,这可以用来直接根据条件渲染元素。


import React from "react"
import boxes from "../public/components/boxes";
import Box from "../public/components/Box";

export default function App(){

  const [messages, setMessages] = React.useState(["a", "b", "c"])
  return (
    <div>
      {
        messages.length > 0 &&
        <h1>You have {messages.length} unread messages!</h1>
      }
    </div>
  )
 
}

12. Conditional rendering: ternary

在React中,条件渲染是指根据条件来决定是否渲染某些组件或元素。三元运算符(ternary operator)是一种常用的JavaScript表达式,用于基于条件进行快速的“if-else”判断,它在React的条件渲染中也非常有用。

condition ? expressionIfTrue : expressionIfFalse;
  • condition:一个布尔表达式,其结果为true或false。
  • expressionIfTrue:如果condition为true,则返回这个表达式的值。
  • expressionIfFalse:如果condition为false,则返回这个表达式的值。

你可以在JSX中直接使用三元运算符来决定渲染哪个元素或组件。

import React from "react"
import boxes from "../public/components/boxes";
import Box from "../public/components/Box";

export default function App(){
  const [messages, setMessages] = React.useState(["a"])
  return (
    <div>
      {
        messages.length === 0 ?
        <h1>You're all caught up!</h1> :
        <h1>You have {messages.length} unread {messages.length > 1 ? "messages" : "message"}</h1>
      }
    </div>
  )
  
}

13. Conditional rendering

  1. What is “conditional rendering”?
    When we want to only sometimes display something on the page
    based on a condition of some sort

  2. When would you use &&?
    When you want to either display something or NOT display it

  3. When would you use a ternary?
    When you need to decide which thing among 2 options to display

  4. What if you need to decide between > 2 options on
    what to display?
    Use an if...else if... else conditional or a switch statement

14. Watch for input changes in React

在React中,监视输入变化是一个常见的需求,尤其是在处理表单时。这可以通过几种方式实现,包括使用状态(state)和效果(effects)。
使用State和Effects监视输入变化
在React中,你可以通过维护一个状态来监视输入的变化。当输入变化时,更新这个状态,从而触发组件的重新渲染。


import React from "react"


export default function App(){


  const [firstName, setFirstName] = React.useState("")

  console.log(firstName)

  function handleChange(event){
    setFirstName(event.target.value)
  }

  return (
    <form>
      <input
        type="text"
        placeholder="First Name"
        onChange={handleChange}
      />
    </form>
  )
  
}

在这个例子中,每次用户输入时,handleChange函数都会被调用,并更新firstName状态,这会导致组件重新渲染并显示最新的输入值。

15. Form state object


import React from "react"


export default function App(){


  const [formData, setFormData] = React.useState(
    {firstName: "", lastName: "", email: ""}
  )

  console.log(formData)

  function handleChange(event){
    setFormData(prevFormData => {
      return {
        ...prevFormData,
        [event.target.name]: event.target.value
      }
    })
  }

  return (
    <form>
      <input
        type="text"
        placeholder="First Name"
        onChange={handleChange}
        name="firstName"
      />
      <input
        type="text"
        placeholder="Last Name"
        onChange={handleChange}
        name="lastName"
      />
      <input
        type="email"
        placeholder="Email"
        onChange={handleChange}
        name="email"
      />
    </form>
  )

  

  
}

16. Forms in React: textarea


import React from "react"


export default function App(){


  const [formData, setFormData] = React.useState(
    {firstName: "", lastName: "", email: "", comments: ""}
  )

  console.log(formData.comments)

  function handleChange(event){
    setFormData(prevFormData => {
      return {
        ...prevFormData,
        [event.target.name]: event.target.value
      }
    })
  }

  return (
    <form>
      <input
        type="text"
        placeholder="First Name"
        onChange={handleChange}
        name="firstName"
        value={formData.firstName}
      />
      <input
        type="text"
        placeholder="Last Name"
        onChange={handleChange}
        name="lastName"
        value={formData.lastName}
      />
      <input
        type="email"
        placeholder="Email"
        onChange={handleChange}
        name="email"
        value={formData.email}
      />
      <textarea
        value={formData.comments}
        placeholder="Comments"
        onChange={handleChange}
        name="comments"
      />
    </form>
  )

  

  
}

17. Forms in React: checkbox


import React from "react"


export default function App(){

  const [formData, setFormData] = React.useState(
    {
      firstName: "", 
      lastName: "", 
      email: "", 
      comments: "",
      isFriendly: true
    }
  )

  function handleChange(event){
    const {name, value, type, checked} = event.target
    setFormData(prevFormData => {
      return {
        ...prevFormData,
        [name]: type === "checkbox" ? checked : value
      }
    })
  }

  return (
    <form>
      <input
        type="text"
        placeholder="First Name"
        onChange={handleChange}
        name="firstName"
        value={formData.firstName}
      />
      <input
        type="text"
        placeholder="Last Name"
        onChange={handleChange}
        name="lastName"
        value={formData.lastName}
      />
      <input
        type="email"
        placeholder="Email"
        onChange={handleChange}
        name="email"
        value={formData.email}
      />
      <textarea
        value={formData.comments}
        placeholder="Comments"
        onChange={handleChange}
        name="comments"
      />
      <input
        type="checkbox"
        id="isFriendly"
        checked={formData.isFriendly}
        onChange={handleChange}
        name="isFriendly"
      />
      <label htmlFor="isFriendly">Are you friendly?</label>
      <br />
    </form>
  )

  

  
}

18. Forms in React: radio buttons


import React from "react"


export default function App(){

  const [formData, setFormData] = React.useState(
    {
      firstName: "", 
      lastName: "", 
      email: "", 
      comments: "",
      isFriendly: true,
      employment: ""
    }
  )

  console.log(formData.employment)

  function handleChange(event){
    const {name, value, type, checked} = event.target
    setFormData(prevFormData => {
      return {
        ...prevFormData,
        [name]: type === "checkbox" ? checked : value
      }
    })
  }

  return (
    <form>
      <input
        type="text"
        placeholder="First Name"
        onChange={handleChange}
        name="firstName"
        value={formData.firstName}
      />
      <input
        type="text"
        placeholder="Last Name"
        onChange={handleChange}
        name="lastName"
        value={formData.lastName}
      />
      <input
        type="email"
        placeholder="Email"
        onChange={handleChange}
        name="email"
        value={formData.email}
      />
      <textarea
        value={formData.comments}
        placeholder="Comments"
        onChange={handleChange}
        name="comments"
      />
      <input
        type="checkbox"
        id="isFriendly"
        checked={formData.isFriendly}
        onChange={handleChange}
        name="isFriendly"
      />
      <label htmlFor="isFriendly">Are you friendly?</label>
      <br />
      <br />

      <fieldset>
        <legend>Current employment status</legend>

        <input 
          type="radio"
          id="unemployed"
          name="employment"
          value="unemployed"
          checked={formData.employment === "unemployed"}
          onChange={handleChange}
        />
        <label htmlFor="unemployed">Unemployed</label>
        <br />

        <input 
          type="radio"
          id="part-time"
          name="employment"
          value="part-time"
          checked={formData.employment === "part-time"}
          onChange={handleChange}
        />
        <label htmlFor="part-time">Part-time</label>
        <br />

        <input 
          type="radio"
          id="full-time"
          name="employment"
          value="full-time"
          checked={formData.employment === "full-time"}
          onChange={handleChange}
        />
        <label htmlFor="full-time">Full-time</label>
        <br />


      </fieldset>
    </form>
  )

  

  
}

19. Forms in React: Select and options


import React from "react"


export default function App(){

  const [formData, setFormData] = React.useState(
    {
      firstName: "", 
      lastName: "", 
      email: "", 
      comments: "",
      isFriendly: true,
      employment: "",
      favColor: ""
    }
  )

  console.log(formData.favColor)

  function handleChange(event){
    const {name, value, type, checked} = event.target
    setFormData(prevFormData => {
      return {
        ...prevFormData,
        [name]: type === "checkbox" ? checked : value
      }
    })
  }

  return (
    <form>
      <input
        type="text"
        placeholder="First Name"
        onChange={handleChange}
        name="firstName"
        value={formData.firstName}
      />
      <input
        type="text"
        placeholder="Last Name"
        onChange={handleChange}
        name="lastName"
        value={formData.lastName}
      />
      <input
        type="email"
        placeholder="Email"
        onChange={handleChange}
        name="email"
        value={formData.email}
      />
      <textarea
        value={formData.comments}
        placeholder="Comments"
        onChange={handleChange}
        name="comments"
      />
      <input
        type="checkbox"
        id="isFriendly"
        checked={formData.isFriendly}
        onChange={handleChange}
        name="isFriendly"
      />
      <label htmlFor="isFriendly">Are you friendly?</label>
      <br />
      <br />

      <fieldset>
        <legend>Current employment status</legend>

        <input 
          type="radio"
          id="unemployed"
          name="employment"
          value="unemployed"
          checked={formData.employment === "unemployed"}
          onChange={handleChange}
        />
        <label htmlFor="unemployed">Unemployed</label>
        <br />

        <input 
          type="radio"
          id="part-time"
          name="employment"
          value="part-time"
          checked={formData.employment === "part-time"}
          onChange={handleChange}
        />
        <label htmlFor="part-time">Part-time</label>
        <br />

        <input 
          type="radio"
          id="full-time"
          name="employment"
          value="full-time"
          checked={formData.employment === "full-time"}
          onChange={handleChange}
        />
        <label htmlFor="full-time">Full-time</label>
        <br />
        </fieldset>

        <label htmlFor="favColor">What is your favorite color?</label>
        <br />
        <select 
          id="favColor"
          value={formData.favColor}
          onChange={handleChange}
          name="favColor"
        >
          <option value="">-- Choose --</option>
          <option value="red">Red</option>
          <option value="orange">Orange</option>
          <option value="yellow">Yellow</option>
          <option value="green">Green</option>
          <option value="blue">Blue</option>
          <option value="indigo">Indigo</option>
          <option value="violet">Violet</option>
        </select>


      
    </form>
  )

  

  
}

20. Forms in React: Submitting the form


import React from "react"


export default function App(){

  const [formData, setFormData] = React.useState(
    {
      firstName: "", 
      lastName: "", 
      email: "", 
      comments: "",
      isFriendly: true,
      employment: "",
      favColor: ""
    }
  )


  function handleChange(event){
    const {name, value, type, checked} = event.target
    setFormData(prevFormData => {
      return {
        ...prevFormData,
        [name]: type === "checkbox" ? checked : value
      }
    })
  }

  function handleSubmit(event) {
    event.preventDefault()
    console.log(formData)
  }

  return (
    <form onSubmit={handleSubmit}>
      <input
        type="text"
        placeholder="First Name"
        onChange={handleChange}
        name="firstName"
        value={formData.firstName}
      />
      <input
        type="text"
        placeholder="Last Name"
        onChange={handleChange}
        name="lastName"
        value={formData.lastName}
      />
      <input
        type="email"
        placeholder="Email"
        onChange={handleChange}
        name="email"
        value={formData.email}
      />
      <textarea
        value={formData.comments}
        placeholder="Comments"
        onChange={handleChange}
        name="comments"
      />
      <input
        type="checkbox"
        id="isFriendly"
        checked={formData.isFriendly}
        onChange={handleChange}
        name="isFriendly"
      />
      <label htmlFor="isFriendly">Are you friendly?</label>
      <br />
      <br />

      <fieldset>
        <legend>Current employment status</legend>

        <input 
          type="radio"
          id="unemployed"
          name="employment"
          value="unemployed"
          checked={formData.employment === "unemployed"}
          onChange={handleChange}
        />
        <label htmlFor="unemployed">Unemployed</label>
        <br />

        <input 
          type="radio"
          id="part-time"
          name="employment"
          value="part-time"
          checked={formData.employment === "part-time"}
          onChange={handleChange}
        />
        <label htmlFor="part-time">Part-time</label>
        <br />

        <input 
          type="radio"
          id="full-time"
          name="employment"
          value="full-time"
          checked={formData.employment === "full-time"}
          onChange={handleChange}
        />
        <label htmlFor="full-time">Full-time</label>
        <br />
        </fieldset>

        <label htmlFor="favColor">What is your favorite color?</label>
        <br />
        <select 
          id="favColor"
          value={formData.favColor}
          onChange={handleChange}
          name="favColor"
        >
          <option value="">-- Choose --</option>
          <option value="red">Red</option>
          <option value="orange">Orange</option>
          <option value="yellow">Yellow</option>
          <option value="green">Green</option>
          <option value="blue">Blue</option>
          <option value="indigo">Indigo</option>
          <option value="violet">Violet</option>
        </select>
        <br />
        <br />
        <button>Submit</button>


      
    </form>
  )

  

  
}

21. Sign up form practice


import React from "react"


export default function App(){

  const [formData, setFormData] = React.useState({
    email: "",
    password: "",
    passwordConfirm: "",
    joinedNewsletter: true
  })

  function handleChange(event){
    const {name, value, type, checked} = event.target
    setFormData(prevFormData => ({
      ...prevFormData,
      [name]: type === "checkbox" ? checked : value
    }))
  }

  function handleSubmit(event){
    event.preventDefault()
    if (formData.password === formData.passwordConfirm){
      console.log("Successfully signed up")
    } else {
      console.log("Passwords do not match")
      return
    }

    if(formData.joinedNewsletter){
      console.log("Thanks for signing up for our newsletter!")
    }
  }

  return (
    <div>
      <form onSubmit={handleSubmit}>
        <input 
          type="email"
          placeholder="Email address"
          name="email"
          onChange={handleChange}
          value={formData.email}
        />
        <input 
          type="password"
          placeholder="Password"
          name="password"
          onChange={handleChange}
          value={formData.password}
        />
        <input 
          type="password"
          placeholder="Confirm password"
          name="passwordConfirm"
          onChange={handleChange}
          value={formData.passwordConfirm}
        />

        <div>
          <input 
            id="okayToEmail"
            type="checkbox"
            name="joinedNewsletter"
            onChange={handleChange}
            checked={formData.joinedNewsletter}
          />
          <label htmlFor="okayToEmail">I want to join the newsletter</label>
        </div>
        <button>Sign up</button>
      </form>
    </div>
  )

  

  
}