JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="input-wrap">
    <input class="input" type="text"><button class="new-btn">新增</button>
  </div>
  
  <ul class="lists">
    <li class="list-title"><span>代辦事項</span><button class="export">匯出</button></li>
  </ul>
  
</div>

SCSS

* {
  box-sizing: border-box;
}

.container {
  max-width: fit-content;
  margin: 30px auto;
  
  .input-wrap {
    display: flex;
    align-items: center;

    
    .input {
      border-top-left-radius: 8px;
      border-bottom-left-radius: 8px;
      font-size: 2rem;
      height: 2.5rem;
      padding: 10px;
      background-color: #aaa;
      max-width: fit-content;
      border: none;
      outline: none;
    }

    .new-btn {
      height: 2.5rem;
      background-color: #aaa;
      border-top-right-radius: 8px;
      border-bottom-right-radius: 8px;
      border: none;
      white-space: nowrap;
      cursor: pointer;
      font-weight: bold;
      font-size: 18px;
      color: #fff;
      transition: color .5s;
      
      &:hover {
        color: #000;
      }
    }
  }
  
  .lists {
    margin-top: 20px;
    background-color: #aaa;
    border-radius: 8px;
    padding: 0 10px 10px 10px;
    
    .list {
      background-color: #ccc;
      font-size: 24px;
      padding: 5px 10px;
      border-radius: 8px;
      height: 2.5rem;
      display: flex;
      justify-content: space-between;
      
      & + li {
        margin-top: 10px;
      }
      
      span {
        color: #000;
      }
      
      .del-btn {
        background-color: transparent;
        border: none;
        color: #fff;
        font-weight: bold;
        font-size: 18px;
        transition: color 0.5s;
        cursor: pointer;
        
        &:hover {
          color: #f00;
        }
      }
    }
    
    .list-title {
      text-align: center;
      padding: 8px 0;
      border-bottom: 1px solid #000;
      margin-bottom: 8px;
      position: relative;
      
      span {
        font-size: 24px;
        font-weight: bold;
      }
      
      .export {
        font-size: 18px;
        background-color: transparent;
        color: #fff;
        border: none;
        position: absolute;
        right: 0;
        top: 10px;
        cursor: pointer;
        
        &:hover {
   ...

JavaScript

const input = document.querySelector('.input');
const lists = document.querySelector('.lists');
const newButton = document.querySelector('.new-btn');
const exports = document.querySelector('.export');
let todoLists = [];

function add() {
	let todoText = input.value;  
  
  if (todoText.trim() === '') return;
  
  let list = document.createElement('li');
  let span = document.createElement('span');  
  let deleteButton = document.createElement('button');
  
  list.classList.add('list');  
  span.textContent = todoText;
  deleteButton.classList.add('del-btn');
  deleteButton.textContent = '刪除'
  deleteButton.onclick = remove;
  
  lists.append(list);
  list.append(span);
  list.append(deleteButton);
  
  todoLists.push(todoText);

  document.querySelector('.input').value = '';
}

function remove() {
	let deleteIndex = todoLists.indexOf(event.target.parentElement.children[0].textContent);
  todoLists.splice(deleteIndex, 1)
	event.target.parentElement.remove();
}

function exportArray() {
	let result = ''
	for (let i = 0; i < todoLists.length; i++) {
  	result += `${i + 1}. ${todoLists[i]}, `    
  }
  if (result === '') return alert('無代辦事項');
	alert(`今日待辦：${result}`);
}

newButton.onclick = add;
exports.onclick = exportArray;