如何在react中添加dark class刷新后保存

Question

how i can save dark class after refresh

import Image from 'next/image'
import React from 'react'

function Theme() {
  
  const toggleMode = (mode) => {
    if (mode === "add") {
      document.documentElement.classList.add("dark");
    } else {
      document.documentElement.classList.remove("dark");
    }
  };
  const mode = localStorage.getItem("mode");
  return (
    <div className="theme_toggle">
        <div className="day_mode flex items-center" onClick={() => toggleMode("add")} >
          <Image src="/dark.svg" width="20" height="20" alt="night_mood" />
        </div>
        <div className="night_mode flex items-center" onClick={() => toggleMode("remove")} >
          <Image src="/day_white.svg" width="20" height="20" alt="day_mood" />
        </div>
    </div>
  )
}

export default Theme

i am adding the cdark class to html tage but i want after refresh it will be save.

Answer 1

simply save and get it from localStorage and apply it to document in useEffect

sth like this:

function Theme() {


  useEffect(()=>{
    const mode = localStorage.getItem("mode");
  
  
     if(mode){
       document.documentElement.classList.add("dark");
    
     }

   },[])
  
  const toggleMode = (mode) => {
    if (mode === "add") {
      document.documentElement.classList.add("dark");
      localStorage.setItem('mode','dark')
    } else {
      document.documentElement.classList.remove("dark");
      localStorage.removeItem('mode')
      
    }
  };
  return (
    <div className="theme_toggle">
      <div className="day_mode flex items-center" onClick={() => toggleMode("add")} >
        <Image src="/dark.svg" width="20" height="20" alt="night_mood" />
      </div>
      <div className="night_mode flex items-center" onClick={() => toggleMode("remove")} >
        <Image src="/day_white.svg" width="20" height="20" alt="day_mood" />
      </div>
    </div>
  )
}

export default Theme