React中用Styled Components包裹代码后，显示密码按钮功能异常

问题根源 #

你把StyledRegisterContainer和StyledButton这两个styled组件定义在了Register函数组件的内部。每次组件触发重新渲染（比如点击显示/隐藏密码按钮时），这两个组件都会被重新创建。React会将它们识别为全新的组件类型，因此会卸载原有的容器及内部表单元素，再重新挂载新的实例，直接导致密码输入框的内容丢失。

修复方案 #

将所有styled组件的定义移到Register组件的外部，确保组件类型在每次渲染时保持一致，避免不必要的DOM卸载和重建。

修改后的Register.js代码 #

import React from 'react'
import Styled from "styled-components";

// 将styled组件移到组件外部
const StyledButton = Styled.button`
    background-color: ${(props)=>props.bgColor};
    color: white;
    display:${(props)=>props.flag==="1"?"inline-block":"block"};
    width:${(props)=>props.flag==="1"?"45%":"100%"};
    margin:5px;
`;

const StyledRegisterContainer = Styled.div`
    width:600px;
    &:hover {box-shadow:0px 0px 5px grey};
    @media (min-width:0px) and (max-width:600px) {
        width:300px;
    };
`;

export default function Register(props) {
    const btnStyle={
        backgroundColor:"red",
        color:"white",
    }
    let btnText;
    const btnClasses = ["btn","m-1","mt-2"];
    if(props.showPass===true)
    {
        btnStyle.backgroundColor = "green";
        btnText="hide password";
        btnClasses.push("btn-primary");
    }
    else{
        btnText="show password";
        btnClasses.push("btn-danger");
    }

  return (
    <StyledRegisterContainer className='container card mt-4 p-3 '>
        <h1 className='text-center'>
            Registration Form
        </h1>
<form onSubmit={props.submit}>
    <div className='form-group'>
        <label className='control-label' htmlFor='name'>Name:</label>
<input type='text' name='name' className='form-control'/>
    </div>
    <div className='form-group'>
        <label className='control-label' htmlFor='email'>Email:</label>
<input type='email' name='email' className='form-control'/>
    </div>
    <div className='form-group'>
        <label className='control-label' htmlFor='password'>password:</label>
<input  type={props.showPass?"text":"password"} name='password' required className='form-control' />
    </div>
    <button type='submit' className='btn btn-primary mt-2 m-1'>
Register
    </button>
    <button  type ="button" className={btnClasses.join(" ")}  onClick={props.click}>
       
{btnText}
    </button>
    <br/>
    <StyledButton flag="1" bgColor="orange">Login</StyledButton>
    <StyledButton flag="1" bgColor="blue">Login</StyledButton>
    <StyledButton flag="0" bgColor="brown">Login</StyledButton>
</form>
    </StyledRegisterContainer>
  )
}

内容的提问来源于stack exchange，提问作者Hamad Ur Rehman