In the arr.js file I have some images. I wrote a function for shuffling the elements in the array. I want react to render the shuffled images when the component is first mounted and also when the images are clicked.

Here is what I tried:

import styled from "styled-components";
import React, {useState, useEffect} from "react";
import Arr from "../utils/arr";

const MainContainer = styled.div`
    display: grid;
    color: white;
    padding: 1rem;
    margin: auto;
    gap: 1rem;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
`

const Main = () => {
    const [arr, setArr] = useState(Arr)

    const shuffleArrayOnClick = (Arr) => {
        for (let i = Arr.length - 1; i > 0; i--) {
            var j = Math.floor(Math.random() * (i   1));
            var tmp = Arr[i];
            Arr[i] = Arr[j];
            Arr[j] = tmp;
        }
        return Arr;
    }

    useEffect(() => {
        const shuffle = shuffleArrayOnClick(Arr);
        setArr(shuffle);
    })

    return (
        <MainContainer onClick={shuffleArrayOnClick}>
            {arr}
        </MainContainer>
    )
}

export default Main;

The useEffect runs right after the initial render when no dependency array is set. So I expected the images to be shuffled when the component is first mounted. But the shuffle doesn't work when I reload the page. Instead the images get shuffled and re-rendered when I change my code and save it. Also how should I set the onclick function on the array elements? Thanks in advance.

CodePudding user response：

NEVER MODIFY REACT STATE DIRECLY

const shuffleArrayOnClick = (arr) => {
  const Arr = [...arr]
  for (let i = Arr.length - 1; i > 0; i--) {
    var j = Math.floor(Math.random() * (i   1));
    var tmp = Arr[i];
      Arr[i] = Arr[j];
      Arr[j] = tmp;
    }
    return Arr;
}

You probably want to run this useEffect once, not million times

useEffect(() => {
  const shuffle = shuffleArrayOnClick(arr);
  setArr(shuffle);
}, [])