How do i concat an array with a different array which uses of local storage

Question

Datalist is an array I'm trying to concat the boards array with the Datalist array, but when I console it doesn't reflect. On the other hand when I assign Datalist.concat(boards) to a variable it reflects example

const newArr = Datalist.concat(boards);
console.log(newArr)

(main code) please help me review it. Thanks in advance

import React, { useState, useEffect } from 'react';
import Modal from './Modal';
import { Datalist } from '../Data/Boards';

function Boards() {
  const [boards, setboards] = useState(JSON.parse(localStorage.getItem('boards')) || []);
  const [title, settitle] = useState('');
  localStorage.setItem('boards', JSON.stringify(boards));

  Datalist.concat(boards);
  console.log(Datalist);

  const handleChange = (e) => {
    settitle(e.target.value);
  };
  const handleSubmit = () => {
    if (title.length === 0) {
      return;
    }
    setboards((prev) => [...prev, title]);
  };
  return (
    <div>
      <ul id="boards">
        <BoardList boards={boards} />
      </ul>
      <Modal title={title} handleChange={handleChange} handleSubmit={handleSubmit} />
    </div>
  );
}
function BoardList({ boards }) {
  const history = useHistory();
  return (
    <>
      {boards.map((board, index) => (
        <li
          key={index}
          onClick={() => {
            history.push('./workspace');
          }}
        >
          <h3>{board}</h3>
        </li>
      ))}
    </>
  );
}
export default Boards;

Aditya Menon · Accepted Answer · 2020-11-19 09:39:35Z

1

That is the expected behaviour. The concat function does not alter the original arrays. You can read about it in the MDN docs

For your case you should be able to do Datalist = Datalist.concat(boards); and it should work like you're expecting

answered Nov 19, 2020 at 9:39

Aditya Menon

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1 Comment

random_dev Over a year ago

it gives Datalist is not defined, Thanks

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