Функция принимает массив, как вернуть html?

const todoList = [];

const list = document.querySelector('.todo-app__list');

class ItemTemplate {
  listItem(items) {
    return items.map((item) => {
     return `<li data-id="${item.id}" class="todo-app__list-item">
                <input type="checkbox" class="todo-app__list-checkbox">
                <label class="todo-app__list-checkbox-label">
                    ${item.title}
                </label>
                <button class="todo-app__item-destroy"></button>
            </li>`;
    })
    .join("\r\n")
  }
}

const itemTemplate = new ItemTemplate();

document.addEventListener('keyup', function(e) {
  if (e.keyCode === 13) {
    const newId = getNewUserID();
    const text = document.querySelector('.todo-app__input').value.trim();
    document.querySelector('.todo-app__input').value = '';

    todoList.push({
      id: newId,
      title: text,
      completed: false
    });

    list.innerHTML = itemTemplate.listItem(todoList);
  }
});

function getNewUserID() {
  return Date.now();
}

.todo-app {
  display: block;
  margin: 0 auto;
}

.todo-app__title {
  display: block;
  width: 100%;
  font-size: 100px;
  line-height: 0;
  font-weight: 100;
  text-align: center;
  color: rgba(175, 47, 47, 0.15);
}

.todo-app__input-wrapper {
  display: block;
  background: #ffffff;
  position: relative;
  box-shadow: 0 2px 4px 0 rgba(0, 0, 0, 0.2), 0 25px 50px 0 rgba(0, 0, 0, 0.1);
}

.todo-app__input-label {
  width: 550px;
}

.todo-app__input {
  padding: 16px 16px 16px 60px;
  border: none;
  background: rgba(0, 0, 0, 0.003);
  box-shadow: inset 0 -2px 1px rgba(0, 0, 0, 0.03);
  position: relative;
  margin: 0;
  width: 86%;
  font-size: 24px;
  line-height: 1.4em;
  font-weight: inherit;
  font-style: italic;
  opacity: 0.5;
  outline: none;
}

.todo-app__input-checkbox {
  width: 1px;
  height: 1px;
  border: none;
  opacity: 0;
  position: absolute;
  right: 100%;
  bottom: 100%;
  &:checked {}
}

.todo-app__input-checkbox:checked {
  .todo-app__input-checkbox-label::before {
    color: #737373;
  }
}

.todo-app__input-checkbox-label {
  width: 60px;
  height: 34px;
  font-size: 0;
  position: absolute;
  top: 14px;
  left: -13px;
  transform: rotate(90deg);
  cursor: default;
  z-index: 1;
  &::before {
    content: '❯';
    font-size: 22px;
    color: #e6e6e6;
    padding: 10px 27px 10px 27px;
    cursor: default;
  }
}

.todo-app__list-wrapper {
  position: relative;
  z-index: 2;
  border-top: 1px solid #e6e6e6;
}

.todo-app__list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.todo-app__list-item {
  position: relative;
  font-size: 24px;
  border-bottom: 1px solid #ededed;
  &:last-child {
    border-bottom: none;
  }
}

.todo-app__list-item:hover {
  .todo-app__item-destroy {
    display: block;
    color: #af5b5e;
  }
}

.todo-app__list-checkbox {
  margin: auto 0;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  text-align: center;
  position: absolute;
  top: 0;
  bottom: 0;
  appearance: none;
  outline: none;
  background-image: url('data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%22http%3A//www.w3.org/2000/svg%22%20width%3D%2240%22%20height%3D%2240%22%20viewBox%3D%22-10%20-18%20100%20135%22%3E%3Ccircle%20cx%3D%2250%22%20cy%3D%2250%22%20r%3D%2250%22%20fill%3D%22none%22%20stroke%3D%22%23ededed%22%20stroke-width%3D%223%22/%3E%3C/svg%3E');
  background-repeat: no-repeat;
  background-position: center left;
}

.todo-app__list-checkbox:checked {
  background-image: url('data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%22http%3A//www.w3.org/2000/svg%22%20width%3D%2240%22%20height%3D%2240%22%20viewBox%3D%22-10%20-18%20100%20135%22%3E%3Ccircle%20cx%3D%2250%22%20cy%3D%2250%22%20r%3D%2250%22%20fill%3D%22none%22%20stroke%3D%22%23bddad5%22%20stroke-width%3D%223%22/%3E%3Cpath%20fill%3D%22%235dc2af%22%20d%3D%22M72%2025L42%2071%2027%2056l-4%204%2020%2020%2034-52z%22/%3E%3C/svg%3E');
}

.todo-app__list-checkbox-label {
  word-break: break-all;
  padding: 15px 15px 15px 60px;
  display: block;
  line-height: 1.2;
  transition: color 0.4s;
  &_completed {
    color: #d9d9d9;
    text-decoration: line-through;
  }
}

.todo-app__item-destroy {
  display: none;
  background: none;
  border: none;
  outline: none;
  position: absolute;
  top: 0;
  right: 10px;
  bottom: 0;
  width: 40px;
  height: 40px;
  margin: auto 11px;
  font-size: 30px;
  color: #cc9a9a;
  opacity: 0.8;
  transition: all 0.2s ease-out;
}

.todo-app__item-destroy::after {
  content: '×';
}

.todo-app__item-destroy:hover {
  opacity: 1;
}

<label class="todo-app__input-label">
                <input type="checkbox" class="todo-app__input-checkbox">
                <label class="todo-app__input-checkbox-label"></label>
<input class="todo-app__input" placeholder="What needs to be done?" autofocus>
</label>
<div class="todo-app__list-wrapper">
  <ul class="todo-app__list">
  </ul>
</div>