Страница с кнопкой

import './dnd.html';

const homeworkContainer = document.querySelector('#homework-container');

function random(from, to) {
    return perseInt(from + Math.random() * to - from);
}

let currentDrag;
let startX = 0;
let startY = 0;

document.addEventListener('mousemove', (e) => {
    if (currentDrag) {
        currentDrag.style.top = e.clientY - startY + 'px';
        currentDrag.style.left = e.clientX - startX + 'px';
    }
});

export function createDiv() {
    const div = document.createElement('div');
    const minSize = 20;
    const maxSize = 200;
    const maxColor = 0xffffff;

    div.className = 'draggable-div';
    div.style.background = '#' + random(0, maxColor).toString(16);
    console.log(div.style.background);
    div.style.top = random(0, window.innerHeight) + 'px';
    div.style.left = random(0, window.innerWidth) + 'px';
    div.style.width = random(0, minSize + maxSize) + 'px';
    div.style.height = random(0, maxSize + maxSize) + 'px';

    div.addEventListener('mousedown', (e) => {
        currentDrag = div;
        startX = e.offsetX;
        startY = e.offsetY;
    });
    div.addEventListener('mouseup', () => (currentDrag = false));

    return div
}

const addDivButton = homeworkContainer.querySelector('#addDiv');

addDivButton.addEventListener('click', function () {
    const div = createDiv();
    homeworkContainer.appendChild(div);
});

<style>
    .draggable-div {
        position: absolute;
    }
</style>

<div id="app">
    <button id="addDiv">добавить div</button>
</div>