Make loop pause every 100ms for visual effect Javascript

Question

I'm currently building a roulette game. To the simulate wheel spinning I'm use this code:

function getColor(item){
var x = document.getElementById(item);
return x.className;
}

function spin() {
  spinning = true;
  
  for (let i = 0; i < options.length; i++) {
  document.getElementById("wheel").style.backgroundColor = getColor(options[i]);
  document.getElementById("number").innerHTML = options[i];
  
  //sleep for 100ms
  
} 
  spinning = false;
}

It does what I need but it does it too fast so you can't see every number go by. Is there a way to make the program sleep for 100ms every iteration. When I try to use setTimeout it doesn't pause the code. I've looked around at other question but they all say to use the timeout and it doesn't work for me.

Does this answer your question? [How do I add a delay in a JavaScript loop?](https://stackoverflow.com/questions/3583724/how-do-i-add-a-delay-in-a-javascript-loop) — nyjC1v2Pu8, Aug 25 '22 at 21:52

oliverwebr · Answer 1 · 2022-08-25T21:58:46.813

For loops respect asynchronous calls so you make your function async and create a little sleep utility function to wait your desired ms time

function getColor(item){
  var x = document.getElementById(item);
  return x.className;
}

function sleep(time) {
  return new Promise((resolve) => setTimeout(resolve, time));
}

async function spin() {
  spinning = true;
  
  for (let i = 0; i < options.length; i++) {
    document.getElementById("wheel").style.backgroundColor = 
    getColor(options[i]);
    document.getElementById("number").innerHTML = options[i];
  
    await sleep(100)
  
  } 
  spinning = false;
}

score 1 · Accepted Answer · answered Aug 25 '22 at 21:50

setTimeout will actually work for you.

let spinning = false;

const options = [1, 2, 3, 4];

function getColor(item) {
  var x = document.getElementById(item);
  return x.className;
}

function spin() {
  spinning = true;
  const total = options.length;
  const delayMs = 100;
  for (let i = 0; i < total; i++) {
    setTimeout(() => {
      document.getElementById("wheel").style.backgroundColor = getColor(
        options[i]
      );
      document.getElementById("number").innerHTML = options[i];
    }, delayMs * i);
  }
  setTimeout(() => {
    spinning = false;
  }, total * delayMs);
}

spin();

<!DOCTYPE html>
<html>
  <head>
    <title>Parcel Sandbox</title>
    <meta charset="UTF-8" />
  </head>

  <body>
    <div id="app">
      <div>
        <p id="1" class="red" />
        <p id="2" class="yellow" />
        <p id="3" class="orange" />
        <p id="4" class="blue" />
      </div>
      <div id="wheel">
        <div id="number"></div>
      </div>
    </div>

    <script src="src/index.js"></script>
  </body>
</html>

Ethicist · Answer 3 · 2022-08-25T22:05:28.287

I can see that it's solved, I'm leaving this here anyway as an alternative way to do it using setInterval instead since I'd already written this up.

// ...
function spin() {
  spinning = true;
  // essentially simulating the for loop's functionality
  // i->options.length, but with a 100ms delay
  let i = 0;
  const interval = setInterval(() => {
    if (i < options.length) {
      ++i;
      document.getElementById('wheel').style.backgroundColor = getColor(
        options[i]
      );
      document.getElementById('number').innerHTML = options[i];
    } else {
      clearInterval(interval);
      spinning = false;
    }
  }, 100);
}
spin();

Make loop pause every 100ms for visual effect Javascript

3 Answers3