如何在 React JS 中的页面刷新时选中持久复选框？

Question

I'm trying to display checkbox ( that was already checked by the user) as checked after page refresh. I was able to save data of the selected rows in local storage (on check) and remove data on uncheck, but when I refresh the page checkbox displays as unchecked(even if local storage has the data stored in it).

My code is

import React, { useState, useEffect } from "react";

const data = [
  {
    id: "1",
    name: "Jane",
    lastName: "Doe",
    age: "25"
  },
  {
    id: "2",
    name: "James",
    lastName: "Doe",
    age: "40"
  },
  {
    id: "3",
    name: "Alexa",
    lastName: "Doe",
    age: "27"
  },
  {
    id: "4",
    name: "Jane",
    lastName: "Brown",
    age: "40"
  }
];

export default function App() {
  const [peopleInfo] = useState(
    data.map((d) => {
      return {
        select: false,
        id: d.id,
        name: d.name,
        lastName: d.lastName,
        age: d.age
      };
    })
  );

  const [peopleInfoValue, setPeopleInfoValue] = useState(
    localStorage.getItem("selectedPeople") == null
      ? ""
      : JSON.parse(localStorage.getItem("selectedPeople"))
  );

  useEffect(() => {
    localStorage.setItem("selectedPeople", JSON.stringify(peopleInfoValue));
  }, [peopleInfoValue]);

  return (
    <div className="App">
      <table>
        <tr>
          {peopleInfo?.map((d) => {
            return (
              <div
                key={d.id}
                style={{
                  display: "flex",
                  width: "150px"
                }}
              >
                <input
                  style={{ margin: "20px" }}
                  onChange={(e) => {
                    // add to list
                    let checked = e.target.checked;
                    if (checked) {
                      setPeopleInfoValue([
                        ...peopleInfoValue,
                        {
                          select: true,
                          id: d.id,
                          name: d.name,
                          lastName: d.lastName,
                          age: d.age
                        }
                      ]);
                    } else {
                      // to remove from localstorage
                      setPeopleInfoValue(
                        peopleInfoValue.filter((people) => people.id !== d.id)
                      );
                    }
                  }}
                  // checked={d.select}
                  type="checkbox"
                />
                <td style={{ margin: "20px" }}>{d.name}</td>
                <td style={{ margin: "20px" }}>{d.lastName}</td>
                <td style={{ margin: "20px" }}>{d.age}</td>
              </div>
            );
          })}
        </tr>
      </table>
    </div>
  );
}

and codeSandbox

As of now on box check local storage looks like this

When I try to pass d.select to checked like this checked={d.select} ( so when d.select is === true box will be checked) it gets saved in localStorage as select:true but doesn't display checked on refresh. I can't figure out how to keep checked boxes still checked after page refresh. Any help and suggestions are greatly appreciated.

Answer 1

You've got the right idea, but there are errors in your code.

Your main problem is that when you render your component, you are mapping the values of peopleInfo , and when you're loading people to see which values have been checked before page refresh, you load them into peopleInfoValue , which you never actually reference when you're rendering your component. While you are correctly setting local storage, the values in local storage never make there way to the display.

Use @Chris G's version it does what you want and is very nice. It's good to understand why your original code wasn't working though.

Answer 2

Problem

The list below shows the reasons why your checkbox doesn't update when the page refreshes.

• checkbox status(checked) is only handled by onChange event (the status updates only when input value is changed by the UI)
• useEffect only handles setting localStorage value

Solution

Include a method inside useEffect to do the following:

• get localStorage value
• set it to the state 'peopleInfoValue'

Answer 3

I see a lot of problems here.

First: you must need to check when you initialize your state if have something in the localstorage.

Second: every radio or checkbox input must have a conditional check in the property "checked":
<input name="IamCheckbox" type="checkbox" checked={user.select} />

Third: Have a lot forms to intialize this data. You can make a new var to pass to the useState or use the useEffect to check to you and update the state. If I doing this I will make the clear way as possible. Because maybe you had to format the data when you initialize the state.