Why there is a delay on visualization? - reactjs

Question

I am building a sorting visualization. I started with a simple bubble sort. When I sort a small array everything is fine and the visualization looks good no matter the speed, but when I visualize a large array there is a delay and the visualization seems to start a few steps ahead and not showing some of the first steps. Why is it happening?
This is my Code:
import React, { useContext, useState, useEffect } from 'react';
const NUMBER_OF_ELEMENTS = 10;
const DEFAULT_COLOR = 'black';
const COMPARE_COLOR = 'darkred';
const DONE_COLOR = 'green';
const SPEED = 150;
const randomIntFromInterval = (min, max) => {
return Math.floor(Math.random() * (max - min + 1) + min);
}
const Dummy = () => {
const [arr, setArr] = useState([]);
const [numberOfElements, setNumberOfElements] = useState(NUMBER_OF_ELEMENTS);
const timeout_id = [];
useEffect(() => {
generateArray();
}, []);
const reset = () => {
resetColors();
generateArray();
}
const generateArray = () => {
const arr1 = [];
for(let i = 0; i < numberOfElements; i++)
{
arr1[i] = randomIntFromInterval(5, 100);
}
console.log(arr1);
setArr(arr1);
}
const resetColors = () => {
const arrayBars = document.getElementsByClassName('array-bar');
for(let i = 0; i < arrayBars.length; i++) {
arrayBars[i].style.backgroundColor = DEFAULT_COLOR;
}
}
const bubbleSort = (arr, n) => {
let i, j, temp, swapped, delay = 1;
for(i = 0; i < n - 1; i++)
{
swapped = false;
for(j = 0; j < n - i - 1; j++)
{
createColor([j, j + 1], COMPARE_COLOR, delay++);
if(arr[j] > arr[j + 1])
{
// swap arr[j] and arr[j+1]
temp = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = temp;
swapped = true;
createAnimation(j, j + 1, delay++);
}
createColor([j, j + 1], DEFAULT_COLOR, delay++);
}
createColor([n - i - 1], DONE_COLOR, delay++);
// If no two elements were
// swapped by inner loop, then break
if(swapped === false) break;
}
const leftovers = [];
for(let k = 0; k < n - i - 1; k++) {
leftovers.push(k);
}
createColor(leftovers, DONE_COLOR, delay++);
}
const createAnimation = (one, two, delay) => {
const arrayBars = document.getElementsByClassName('array-bar');
const id = setTimeout(() => {
const barOneHeight = arrayBars[one].style.height;
const barTwoHeight = arrayBars[two].style.height;
arrayBars[two].style.height = `${barOneHeight}`;
arrayBars[one].style.height = `${barTwoHeight}`;
}, SPEED * delay);
timeout_id.push(id);
}
const createColor = (indexes, color, delay) => {
const arrayBars = document.getElementsByClassName('array-bar');
const id = setTimeout(() => {
for(let i = 0; i < indexes.length; i++) {
arrayBars[indexes[i]].style.backgroundColor = color;
}
}, SPEED * delay);
timeout_id.push(id);
}
const handleSort = (arr) => {
bubbleSort(arr, arr.length);
}
const handlerRange = (e) => {
setNumberOfElements(e.target.value);
}
const stopTimeOuts =() => {
for(let i = 0; i < timeout_id.length; i++) {
clearTimeout(timeout_id[i]);
}
}
return (
<div>
<div className="array-container">
{arr.map((value, idx) => (
<div className="array-bar"
key={idx}
style={{
backgroundColor: DEFAULT_COLOR,
height: `${value}px`,
width: `${100 / arr.length}%`,
display: 'inline-block',
margin: '0 1px'
}}>
</div>
))}
</div>
<div className="buttons-container">
<button onClick={() => handleSort(arr)}>Sort!</button>
<button onClick={() => reset()}>Reset</button>
<button onClick={() => stopTimeOuts()}>Stop!</button>
</div>
<div className="slider-container">
1
<input type="range"
min="1"
max="100"
onChange={(e) => handlerRange(e)}
className="slider"
id="myRange"
/>
100
</div>
{numberOfElements}
</div>
);
}
export default Dummy;
EDIT: I don't know why but it seems that there are times that the delay occurs and there are times that it isn't. For now I still don't know why and how to handle this.

Answer 1

Almost always when there are performance issues in React it has to do with component being rendered multiple times.
Try to change useEffect like this:
useEffect(() => {
generateArray();
}, [NUMBER_OF_ELEMENTS]);