Set an element attribute multiple times within a javascript function

im using Vanilla Javascript, and my problem is that i need to render a progress bar in a certain time, but JS only render the final step…

'use strict'
var button = document.getElementById('button');

function sleep(milliseconds) {
    const date = Date.now();
    let currentDate = null;
    do {
      currentDate = Date.now();
    } while (currentDate - date < milliseconds);
  }

function initProgressBar()
{
    let progressBar = document.querySelector('#progress-bar'),
    count = 25,
    total = 64;
    progressBar.style = `width:${count}%;`;

    while (total > 0) {
        sleep(300);
        total = Math.trunc(total/2);
        count = count + total;
        progressBar.style = `width:${count}%;`;
        
    }
}

button.onclick = initProgressBar;
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #progress-container {
            height: 4px;
            width: 100%;
        }

        #progress-bar {
            width: 0%;
            height: 100%;
            background-color: blueviolet;
        }


    </style>
</head>
<body>
    <div id="progress-container">
        <div id="progress-bar"></div>
    </div>
    <button id=button>press</button>
    <script src='prueba.js'></script>
</body>
</html>

The idea is that when the user clicks the button, the progress bar automatically jumps to 25% and then progressively goes to ~ 88% (after that I’ll send it to 100% using another function)

The problem is that Javascript only update the element on his last value (88%).

So, is there any way to set the attribute of an element multiple times inside a javasciript function?